diff --git a/org.eclipse.mylyn.tasks.core.tests/src/org/eclipse/mylyn/internal/tasks/core/data/TaskDataStoreTest.java b/org.eclipse.mylyn.tasks.core.tests/src/org/eclipse/mylyn/internal/tasks/core/data/TaskDataStoreTest.java
new file mode 100644
index 0000000..73a9591
--- /dev/null
+++ b/org.eclipse.mylyn.tasks.core.tests/src/org/eclipse/mylyn/internal/tasks/core/data/TaskDataStoreTest.java
@@ -0,0 +1,333 @@
+/*******************************************************************************
+ * Copyright (c) 2017 Tasktop Technologies and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Tasktop Technologies - initial API and implementation
+ *******************************************************************************/
+
+package org.eclipse.mylyn.internal.tasks.core.data;
+
+import static java.lang.String.format;
+import static java.util.stream.Collectors.toList;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CyclicBarrier;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipOutputStream;
+
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.mylyn.internal.tasks.core.TaskRepositoryManager;
+import org.eclipse.mylyn.tasks.core.TaskRepository;
+import org.eclipse.mylyn.tasks.core.data.ITaskDataWorkingCopy;
+import org.eclipse.mylyn.tasks.core.data.TaskAttributeMapper;
+import org.eclipse.mylyn.tasks.core.data.TaskData;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.xml.sax.SAXException;
+
+import com.google.common.base.Charsets;
+import com.google.common.io.ByteStreams;
+
+public class TaskDataStoreTest {
+
+	@Rule
+	public TemporaryFolder folder = new TemporaryFolder();
+
+	private static final int THREAD_COUNT = 10;
+
+	private static final long DELAY = 100;
+
+	private static final String DATA_XML_CONTENT = "test";
+
+	private static final TaskData TASK_DATA = newTaskData();
+
+	private static final TaskDataState TEST_STATE = new TaskDataState("connectorKind", "repositoryUrl", "taskId");
+
+	@Test
+	public void getTaskDataStateByMultipleThreads() throws Exception {
+		File file = newTaskDataZipFile();
+
+		List<Throwable> failures = runSameByMultipleThreads(getTaskDataState(file));
+
+		assertNoFailures(failures);
+	}
+
+	@Test
+	public void discardEditsByMultipleThreads() throws Exception {
+		File file = newTaskDataZipFile();
+
+		List<Throwable> failures = runSameByMultipleThreads(discardEdits(file));
+
+		assertNoFailures(failures);
+	}
+
+	@Test
+	public void putEditsByMultipleThreads() throws Exception {
+		File file = newTaskDataZipFile();
+
+		List<Throwable> failures = runSameByMultipleThreads(putEdits(file));
+
+		assertNoFailures(failures);
+	}
+
+	@Test
+	public void putTaskDataSetLastReadUserByMultipleThreads() throws Exception {
+		File file = newTaskDataZipFile();
+
+		List<Throwable> failures = runSameByMultipleThreads(putTaskData(file));
+
+		assertNoFailures(failures);
+	}
+
+	@Test
+	public void setTaskDataByMultipleThreads() throws Exception {
+		File file = newTaskDataZipFile();
+
+		List<Throwable> failures = runSameByMultipleThreads(setTaskData(file));
+
+		assertNoFailures(failures);
+	}
+
+	@Test
+	public void putTaskDataByMultipleThreads() throws Exception {
+		File file = newTaskDataZipFile();
+
+		List<Throwable> failures = runSameByMultipleThreads(putTaskDataState(file));
+
+		assertNoFailures(failures);
+	}
+
+	@Test
+	public void deleteTaskDataByMultipleThreads() throws Exception {
+		File file = newTaskDataZipFile();
+
+		List<Throwable> failures = runSameByMultipleThreads(deleteTaskData(file));
+
+		assertNoFailures(failures);
+	}
+
+	@Test
+	public void manipulateTaskDataConcurrently() throws Exception {
+		File file = newTaskDataZipFile();
+
+		// run multiple times to increase chance of a failure
+		for (int i = 0; i <= 10; i++) {
+			List<Throwable> failures = runConcurrently( //
+					getTaskDataState(file), //
+					discardEdits(file), //
+					putEdits(file), //
+					putTaskData(file), //
+					setTaskData(file), //
+					putTaskDataState(file), //
+					deleteTaskData(file));
+			assertNoFailures(failures);
+		}
+	}
+
+	@Test
+	public void manipulateTaskDataByFixedNumberOfThreads() throws Exception {
+		File file = newTaskDataZipFile();
+		TaskDataStore store = newTaskDataStore();
+		List<Throwable> failures = new ArrayList<>();
+		ExecutorService executor = Executors.newFixedThreadPool(4);
+
+		List<Thread> threads = new ArrayList<>();
+		threads.addAll(Collections.nCopies(3, thread(getTaskDataState(file), store, Optional.empty(), failures).get()));
+		threads.addAll(Collections.nCopies(3, thread(discardEdits(file), store, Optional.empty(), failures).get()));
+		threads.addAll(Collections.nCopies(3, thread(putEdits(file), store, Optional.empty(), failures).get()));
+		threads.addAll(Collections.nCopies(3, thread(putTaskData(file), store, Optional.empty(), failures).get()));
+		threads.addAll(Collections.nCopies(3, thread(setTaskData(file), store, Optional.empty(), failures).get()));
+		threads.addAll(Collections.nCopies(3, thread(putTaskDataState(file), store, Optional.empty(), failures).get()));
+		threads.addAll(Collections.nCopies(3, thread(deleteTaskData(file), store, Optional.empty(), failures).get()));
+		Collections.shuffle(threads);
+
+		threads.stream().forEach(thread -> executor.submit(thread));
+
+		executor.shutdown();
+
+		assertTrue(executor.awaitTermination(30, TimeUnit.SECONDS));
+		assertNoFailures(failures);
+	}
+
+	private static TaskDataStore newTaskDataStore() {
+		TaskRepositoryManager manager = new TaskRepositoryManager();
+		TaskDataExternalizer externalizer = new TaskDataExternalizer(manager) {
+			@Override
+			public TaskDataState readState(InputStream in) throws IOException, SAXException {
+				// read the input stream fully but do not return the result, not relevant for the purpose of the test
+				assertEquals(DATA_XML_CONTENT, new String(ByteStreams.toByteArray(in), Charsets.UTF_8));
+				in.close();
+				// pretend that reading state takes more than the blink of an eye
+				sleep();
+				return TEST_STATE;
+			};
+
+			@Override
+			public void writeState(OutputStream out, ITaskDataWorkingCopy state) throws IOException {
+				out.write(DATA_XML_CONTENT.getBytes(Charsets.UTF_8));
+				// pretend that writing state takes more than the blink of an eye
+				sleep();
+			}
+		};
+		return new TaskDataStore(externalizer);
+	}
+
+	private static void sleep() {
+		try {
+			Thread.sleep(DELAY);
+		} catch (InterruptedException e) {
+			Thread.currentThread().interrupt();
+			throw new RuntimeException(e);
+		}
+	}
+
+	private File newTaskDataZipFile() throws IOException {
+		File file = folder.newFile("test.zip");
+		try (ZipOutputStream outputStream = new ZipOutputStream(new FileOutputStream(file))) {
+			ZipEntry entry = new ZipEntry("data.xml");
+			outputStream.putNextEntry(entry);
+			byte[] data = DATA_XML_CONTENT.getBytes();
+			outputStream.write(data, 0, data.length);
+			outputStream.closeEntry();
+		}
+		return file;
+	}
+
+	private static TaskData newTaskData() {
+		TaskRepository repository = new TaskRepository("connectorKind", "repositoryUrl");
+		TaskAttributeMapper mapper = new TaskAttributeMapper(repository);
+		return new TaskData(mapper, "connectorKind", "repositoryUrl", "taskId");
+	}
+
+	@FunctionalInterface
+	public interface ConsumerWithCoreException<T> {
+		public void accept(T t) throws CoreException;
+	}
+
+	private ConsumerWithCoreException<TaskDataStore> getTaskDataState(File file) {
+		return store -> store.getTaskDataState(file);
+	}
+
+	private ConsumerWithCoreException<TaskDataStore> discardEdits(File file) {
+		return store -> store.discardEdits(file);
+	}
+
+	private ConsumerWithCoreException<TaskDataStore> putEdits(File file) {
+		return store -> store.putEdits(file, TASK_DATA);
+	}
+
+	private ConsumerWithCoreException<TaskDataStore> putTaskData(File file) {
+		return store -> store.putTaskData(file, TASK_DATA, true, true);
+	}
+
+	private ConsumerWithCoreException<TaskDataStore> setTaskData(File file) {
+		return store -> store.setTaskData(file, TASK_DATA);
+	}
+
+	private ConsumerWithCoreException<TaskDataStore> putTaskDataState(File file) {
+		return store -> store.putTaskData(file, TEST_STATE);
+	}
+
+	private ConsumerWithCoreException<TaskDataStore> deleteTaskData(File file) {
+		return store -> store.deleteTaskData(file);
+	}
+
+	private static List<Throwable> runSameByMultipleThreads(ConsumerWithCoreException<TaskDataStore> consumer)
+			throws Exception {
+		TaskDataStore store = newTaskDataStore();
+		CyclicBarrier barrier = new CyclicBarrier(THREAD_COUNT + 1);
+		List<Throwable> failures = new ArrayList<>(THREAD_COUNT);
+
+		List<Thread> threads = Stream.generate(thread(consumer, store, Optional.of(barrier), failures))
+				.limit(THREAD_COUNT)
+				.collect(toList());
+
+		startThreadsSimultaneously(barrier, threads);
+		return failures;
+	}
+
+	@SafeVarargs
+	private static List<Throwable> runConcurrently(ConsumerWithCoreException<TaskDataStore>... consumers)
+			throws Exception {
+		TaskDataStore store = newTaskDataStore();
+		CyclicBarrier barrier = new CyclicBarrier(consumers.length + 1);
+		List<Throwable> failures = new ArrayList<>(consumers.length);
+
+		List<Thread> threads = Arrays.asList(consumers)
+				.stream()
+				.map(c -> thread(c, store, Optional.of(barrier), failures).get())
+				.collect(toList());
+
+		startThreadsSimultaneously(barrier, threads);
+		return failures;
+	}
+
+	private static void startThreadsSimultaneously(CyclicBarrier barrier, List<Thread> threads) throws Exception {
+		threads.stream().forEach(Thread::start);
+		barrier.await();
+		for (Thread thread : threads) {
+			thread.join();
+		}
+	}
+
+	private static Supplier<Thread> thread(ConsumerWithCoreException<TaskDataStore> consumer, TaskDataStore store,
+			Optional<CyclicBarrier> barrier, List<Throwable> failures) {
+		return new Supplier<Thread>() {
+
+			@Override
+			public Thread get() {
+				return new Thread(new Runnable() {
+
+					@Override
+					public void run() {
+						try {
+							barrier.ifPresent(b -> {
+								try {
+									b.await();
+								} catch (InterruptedException | BrokenBarrierException e) {
+									throw new RuntimeException(e);
+								}
+							});
+							consumer.accept(store);
+						} catch (Throwable e) {
+							failures.add(e);
+						}
+					}
+				});
+			}
+		};
+	}
+
+	private static void assertNoFailures(List<Throwable> failures) {
+		assertTrue(format("expected no failures but found %d:\n%s", failures.size(), collectMessages(failures)),
+				failures.isEmpty());
+	}
+
+	private static String collectMessages(List<Throwable> failures) {
+		return failures.stream().map(e -> e.getClass().getSimpleName()).collect(Collectors.joining("\n"));
+	}
+
+}
diff --git a/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/data/TaskDataStore.java b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/data/TaskDataStore.java
index defad4d..85c6107 100644
--- a/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/data/TaskDataStore.java
+++ b/org.eclipse.mylyn.tasks.core/src/org/eclipse/mylyn/internal/tasks/core/data/TaskDataStore.java
@@ -17,6 +17,8 @@
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipInputStream;
 import java.util.zip.ZipOutputStream;
@@ -40,11 +42,17 @@
 
 	private final TaskDataExternalizer externalizer;
 
+	private final ReadWriteLock lock = new ReentrantReadWriteLock();
+
 	public TaskDataStore(IRepositoryManager taskRepositoryManager) {
-		this.externalizer = new TaskDataExternalizer(taskRepositoryManager);
+		this(new TaskDataExternalizer(taskRepositoryManager));
 	}
 
-	public synchronized TaskDataState discardEdits(File file) throws CoreException {
+	TaskDataStore(TaskDataExternalizer externalizer) {
+		this.externalizer = externalizer;
+	}
+
+	public TaskDataState discardEdits(File file) throws CoreException {
 		TaskDataState state = readState(file);
 		if (state != null) {
 			state.setEditsData(null);
@@ -53,11 +61,11 @@
 		return state;
 	}
 
-	public synchronized TaskDataState getTaskDataState(File file) throws CoreException {
+	public TaskDataState getTaskDataState(File file) throws CoreException {
 		return readState(file);
 	}
 
-	public synchronized void putEdits(File file, TaskData data) throws CoreException {
+	public void putEdits(File file, TaskData data) throws CoreException {
 		Assert.isNotNull(file);
 		Assert.isNotNull(data);
 		TaskDataState state = readState(file);
@@ -68,8 +76,7 @@
 		writeState(file, state);
 	}
 
-	public synchronized TaskDataState putTaskData(File file, TaskData data, boolean setLastRead, boolean user)
-			throws CoreException {
+	public TaskDataState putTaskData(File file, TaskData data, boolean setLastRead, boolean user) throws CoreException {
 		Assert.isNotNull(file);
 		Assert.isNotNull(data);
 		TaskDataState state = null;
@@ -93,7 +100,7 @@
 		return state;
 	}
 
-	public synchronized TaskDataState setTaskData(File file, TaskData data) throws CoreException {
+	public TaskDataState setTaskData(File file, TaskData data) throws CoreException {
 		Assert.isNotNull(file);
 		Assert.isNotNull(data);
 
@@ -123,6 +130,7 @@
 	}
 
 	private TaskDataState readState(File file) throws CoreException {
+		lock.readLock().lock();
 		try {
 			if (file.exists()) {
 				try {
@@ -146,10 +154,13 @@
 		} catch (IOException e) {
 			throw new CoreException(new Status(IStatus.ERROR, ITasksCoreConstants.ID_PLUGIN, "Error reading task data", //$NON-NLS-1$
 					e));
+		} finally {
+			lock.readLock().unlock();
 		}
 	}
 
 	private void writeState(File file, TaskDataState state) throws CoreException {
+		lock.writeLock().lock();
 		try {
 			try (ZipOutputStream out = new ZipOutputStream(new BufferedOutputStream(new FileOutputStream(file)))) {
 				out.setMethod(ZipOutputStream.DEFLATED);
@@ -162,15 +173,22 @@
 		} catch (IOException e) {
 			throw new CoreException(new Status(IStatus.ERROR, ITasksCoreConstants.ID_PLUGIN, "Error writing task data", //$NON-NLS-1$
 					e));
+		} finally {
+			lock.writeLock().unlock();
 		}
 	}
 
-	public synchronized void putTaskData(File file, TaskDataState state) throws CoreException {
+	public void putTaskData(File file, TaskDataState state) throws CoreException {
 		writeState(file, state);
 	}
 
-	public synchronized boolean deleteTaskData(File file) {
-		return file.delete();
+	public boolean deleteTaskData(File file) {
+		lock.writeLock().lock();
+		try {
+			return file.delete();
+		} finally {
+			lock.writeLock().unlock();
+		}
 	}
 
 }