diff --git a/test-server/java-tests/src/it/java/software/amazon/encryption/s3/RoundTripTests.java b/test-server/java-tests/src/it/java/software/amazon/encryption/s3/RoundTripTests.java
index 6a16ba7b..a94c561c 100644
--- a/test-server/java-tests/src/it/java/software/amazon/encryption/s3/RoundTripTests.java
+++ b/test-server/java-tests/src/it/java/software/amazon/encryption/s3/RoundTripTests.java
@@ -52,7 +52,7 @@ public static void setup() {
     @MethodSource("software.amazon.encryption.s3.TestUtils#crossLanguageClients")
     public void crossLanguageTestKms(LanguageServerTarget encLang, LanguageServerTarget decLang) {
         S3ECTestServerClient encClient = testServerClientFor(encLang);
-        final String objectKey = "cross-lang-test-key-" + encLang;
+        final String objectKey = appendTestSuffix("cross-lang-test-key-" + encLang);
         final String input = "simple-test-input";
         KeyMaterial kmsKeyArn = KeyMaterial.builder()
           .kmsKeyId(KMS_KEY_ARN)
@@ -92,7 +92,7 @@ public void crossLanguageTestKmsWithEncCtx(LanguageServerTarget encLang, Languag
             return;
         }
         S3ECTestServerClient encClient = testServerClientFor(encLang);
-        final String objectKey = "cross-lang-test-key-kms-ec-" + encLang;
+        final String objectKey = appendTestSuffix("cross-lang-test-key-kms-ec-" + encLang);
         final String input = "simple-test-input";
         final Map<String, String> encCtx = new HashMap<>();
         encCtx.put("user-defined-enc-ctx-key", "user-defined-enc-ctx-value");
@@ -142,7 +142,7 @@ public void crossLanguageTestKmsWithSubsetEncCtxFails(LanguageServerTarget encLa
             return;
         }
         S3ECTestServerClient encClient = testServerClientFor(encLang);
-        final String objectKey = "cross-lang-test-key-kms-ec-subset-fails" + encLang;
+        final String objectKey = appendTestSuffix("cross-lang-test-key-kms-ec-subset-fails" + encLang);
         final String input = "simple-test-input";
         final Map<String, String> encCtx = new HashMap<>();
         encCtx.put("user-defined-enc-ctx-key", "user-defined-enc-ctx-value");
@@ -193,7 +193,7 @@ public void crossLanguageTestKmsWithIncorrectEncCtxFails(LanguageServerTarget en
             return;
         }
         S3ECTestServerClient encClient = testServerClientFor(encLang);
-        final String objectKey = "cross-lang-test-key-kms-ec-incorrect-fails" + encLang;
+        final String objectKey = appendTestSuffix("cross-lang-test-key-kms-ec-incorrect-fails" + encLang);
         final String input = "simple-test-input";
         final Map<String, String> encCtx = new HashMap<>();
         encCtx.put("user-defined-enc-ctx-key", "user-defined-enc-ctx-value");
@@ -246,7 +246,7 @@ public void crossLanguageTestKmsWithIncorrectEncCtxFails(LanguageServerTarget en
     @MethodSource("software.amazon.encryption.s3.TestUtils#clientsForTest")
     public void kmsV1Legacy(String language) {
         S3ECTestServerClient client = testServerClientFor(getServerMap().get(language));
-        final String objectKey = "test-key-kms-v1-" + language;
+        final String objectKey = appendTestSuffix("test-key-kms-v1-" + language);
         final String input = "simple-test-input";
         KeyMaterial kmsKeyArn = KeyMaterial.builder()
           .kmsKeyId(KMS_KEY_ARN)
@@ -288,7 +288,7 @@ public void kmsV1Legacy(String language) {
     @MethodSource("software.amazon.encryption.s3.TestUtils#clientsForTest")
     public void kmsV1LegacyWithEncCtx(String language) {
         S3ECTestServerClient client = testServerClientFor(getServerMap().get(language));
-        final String objectKey = "test-key-kms-v1-with-enc-ctx-" + language;
+        final String objectKey = appendTestSuffix("test-key-kms-v1-with-enc-ctx-" + language);
         final String input = "simple-test-input";
         KeyMaterial kmsKeyArn = KeyMaterial.builder()
           .kmsKeyId(KMS_KEY_ARN)
@@ -337,7 +337,7 @@ public void kmsV1LegacyWithEncCtx(String language) {
     @MethodSource("software.amazon.encryption.s3.TestUtils#clientsForTest")
     public void kmsV1LegacyFailsWhenLegacyDisabled(String language) {
         S3ECTestServerClient client = testServerClientFor(getServerMap().get(language));
-        final String objectKey = "test-key-kms-v1-fails-disabled" + language;
+        final String objectKey = appendTestSuffix("test-key-kms-v1-fails-disabled" + language);
         final String input = "simple-test-input";
         KeyMaterial kmsKeyArn = KeyMaterial.builder()
           .kmsKeyId(KMS_KEY_ARN)
diff --git a/test-server/java-tests/src/it/java/software/amazon/encryption/s3/TestUtils.java b/test-server/java-tests/src/it/java/software/amazon/encryption/s3/TestUtils.java
index 3237ee72..62371b56 100644
--- a/test-server/java-tests/src/it/java/software/amazon/encryption/s3/TestUtils.java
+++ b/test-server/java-tests/src/it/java/software/amazon/encryption/s3/TestUtils.java
@@ -17,6 +17,8 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import org.joda.time.DateTime;
+import org.joda.time.format.DateTimeFormat;
 import org.junit.jupiter.params.provider.Arguments;
 import com.amazonaws.regions.Region;
 import com.amazonaws.regions.Regions;
@@ -316,4 +318,17 @@ public static Stream<Arguments> crossLanguageClients() {
                     Arguments.of(t1, t2)
                 )));
     }
+
+    /**
+     * For a given string, append a suffix to distinguish it from
+     * simultaneous test runs.
+     * @param s The string to append the suffix to
+     * @return The string with the suffix appended
+     */
+    public static String appendTestSuffix(final String s) {
+        StringBuilder stringBuilder = new StringBuilder(s);
+        stringBuilder.append(DateTimeFormat.forPattern("-yyMMdd-hhmmss-").print(new DateTime()));
+        stringBuilder.append((int) (Math.random() * 100000));
+        return stringBuilder.toString();
+    }
 }