diff --git a/CHANGELOG.md b/CHANGELOG.md
index af4bac6c19..1afe1bfd0b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -41,6 +41,8 @@ to docs, or any other relevant information.
   specific to the Temporal CLI dev server implementation and may no longer be valid if that implementation changes.
 
 ### Fixed
+- `RetryOptions.merge` now accepts partially configured policies, preserving unset initial intervals
+  and backoff coefficients until validation or annotation merging supplies them.
 - Test server now honors retry expiration deadlines that fall exactly on a whole second. Previously such deadlines were
   ignored and retries were scheduled past them instead of failing with `RETRY_STATE_TIMEOUT`.
 
diff --git a/temporal-sdk/src/main/java/io/temporal/common/RetryOptions.java b/temporal-sdk/src/main/java/io/temporal/common/RetryOptions.java
index 157354cc9c..f4ee0b5a18 100644
--- a/temporal-sdk/src/main/java/io/temporal/common/RetryOptions.java
+++ b/temporal-sdk/src/main/java/io/temporal/common/RetryOptions.java
@@ -77,18 +77,25 @@ public static RetryOptions merge(MethodRetry r, RetryOptions o) {
         .build();
   }
 
-  /** The parameter options takes precedence. */
+  /** The parameter options takes precedence. Unset fields remain unset until validation. */
   public RetryOptions merge(RetryOptions o) {
     if (o == null) {
       return this;
     }
-    return RetryOptions.newBuilder()
-        .setInitialInterval(
-            OptionsUtils.merge(getInitialInterval(), o.getInitialInterval(), Duration.class))
+    RetryOptions.Builder builder = RetryOptions.newBuilder();
+    Duration initial =
+        OptionsUtils.merge(getInitialInterval(), o.getInitialInterval(), Duration.class);
+    if (initial != null) {
+      builder.setInitialInterval(initial);
+    }
+    double coefficient =
+        OptionsUtils.merge(getBackoffCoefficient(), o.getBackoffCoefficient(), double.class);
+    if (coefficient != 0d) {
+      builder.setBackoffCoefficient(coefficient);
+    }
+    return builder
         .setMaximumInterval(
             OptionsUtils.merge(getMaximumInterval(), o.getMaximumInterval(), Duration.class))
-        .setBackoffCoefficient(
-            OptionsUtils.merge(getBackoffCoefficient(), o.getBackoffCoefficient(), double.class))
         .setMaximumAttempts(
             OptionsUtils.merge(getMaximumAttempts(), o.getMaximumAttempts(), int.class))
         .setDoNotRetry(OptionsUtils.merge(getDoNotRetry(), o.getDoNotRetry()))
diff --git a/temporal-sdk/src/test/java/io/temporal/common/RetryOptionsTest.java b/temporal-sdk/src/test/java/io/temporal/common/RetryOptionsTest.java
index ddb873e470..22f66bae4f 100644
--- a/temporal-sdk/src/test/java/io/temporal/common/RetryOptionsTest.java
+++ b/temporal-sdk/src/test/java/io/temporal/common/RetryOptionsTest.java
@@ -1,12 +1,92 @@
 package io.temporal.common;
 
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
 
 import java.time.Duration;
 import org.junit.Test;
 
 public class RetryOptionsTest {
 
+  @Test
+  public void mergeEmptyOptionsPreservesUnsetFields() {
+    RetryOptions merged =
+        RetryOptions.newBuilder().build().merge(RetryOptions.newBuilder().build());
+
+    assertNull(merged.getInitialInterval());
+    assertEquals(0.0, merged.getBackoffCoefficient(), 0.0);
+    assertNull(merged.getMaximumInterval());
+    assertNull(merged.getDoNotRetry());
+    assertEquals(0, merged.getMaximumAttempts());
+    assertEquals(
+        RetryOptions.newBuilder().validateBuildWithDefaults(),
+        merged.toBuilder().validateBuildWithDefaults());
+  }
+
+  @Test
+  public void mergePartialOptionsCombinesExplicitFields() {
+    RetryOptions original = RetryOptions.newBuilder().setMaximumAttempts(3).build();
+    RetryOptions override = RetryOptions.newBuilder().setDoNotRetry("PermanentFailure").build();
+
+    RetryOptions merged = original.merge(override);
+
+    assertEquals(3, merged.getMaximumAttempts());
+    assertArrayEquals(new String[] {"PermanentFailure"}, merged.getDoNotRetry());
+    assertNull(merged.getInitialInterval());
+    assertEquals(0.0, merged.getBackoffCoefficient(), 0.0);
+    assertEquals(
+        Duration.ofSeconds(1), merged.toBuilder().validateBuildWithDefaults().getInitialInterval());
+  }
+
+  @Test
+  public void mergeInitialIntervalWithoutBackoff() {
+    RetryOptions original =
+        RetryOptions.newBuilder().setInitialInterval(Duration.ofSeconds(3)).build();
+    RetryOptions merged = original.merge(RetryOptions.newBuilder().setMaximumAttempts(2).build());
+
+    assertEquals(Duration.ofSeconds(3), merged.getInitialInterval());
+    assertEquals(0.0, merged.getBackoffCoefficient(), 0.0);
+    assertEquals(2.0, merged.toBuilder().validateBuildWithDefaults().getBackoffCoefficient(), 0.0);
+  }
+
+  @Test
+  public void mergeExplicitBackoffWithoutInitialInterval() {
+    RetryOptions merged =
+        RetryOptions.newBuilder()
+            .setBackoffCoefficient(3.0)
+            .build()
+            .merge(RetryOptions.newBuilder().setBackoffCoefficient(4.0).build());
+
+    assertNull(merged.getInitialInterval());
+    assertEquals(4.0, merged.getBackoffCoefficient(), 0.0);
+  }
+
+  @Test
+  public void mergeExplicitFieldsPrefersOverride() {
+    RetryOptions original =
+        RetryOptions.newBuilder()
+            .setInitialInterval(Duration.ofSeconds(2))
+            .setMaximumInterval(Duration.ofSeconds(20))
+            .setBackoffCoefficient(3.0)
+            .setMaximumAttempts(5)
+            .setDoNotRetry("OriginalFailure")
+            .build();
+    RetryOptions override =
+        RetryOptions.newBuilder()
+            .setInitialInterval(Duration.ofSeconds(4))
+            .setMaximumInterval(Duration.ofSeconds(40))
+            .setBackoffCoefficient(4.0)
+            .setMaximumAttempts(6)
+            .setDoNotRetry("OverrideFailure")
+            .build();
+
+    assertEquals(override, original.merge(override));
+    assertEquals(original, original.merge(RetryOptions.newBuilder().build()));
+    assertSame(original, original.merge((RetryOptions) null));
+  }
+
   @Test
   public void mergePrefersTheParameter() {
     RetryOptions o1 =
@@ -28,4 +108,26 @@ public void maximumIntervalCantBeLessThanInitial() {
         .setMaximumInterval(Duration.ofSeconds(1))
         .validateBuildWithDefaults();
   }
+
+  @Test
+  public void mergePartialOptionsPreservesAnnotationValues() throws NoSuchMethodException {
+    MethodRetry annotation =
+        RetryOptionsTest.class.getMethod("annotatedRetry").getAnnotation(MethodRetry.class);
+    RetryOptions merged =
+        RetryOptions.newBuilder()
+            .setMaximumAttempts(3)
+            .build()
+            .merge(RetryOptions.newBuilder().setDoNotRetry("PermanentFailure").build());
+
+    RetryOptions resolved =
+        RetryOptions.merge(annotation, merged).toBuilder().validateBuildWithDefaults();
+
+    assertEquals(Duration.ofSeconds(5), resolved.getInitialInterval());
+    assertEquals(4.0, resolved.getBackoffCoefficient(), 0.0);
+    assertEquals(3, resolved.getMaximumAttempts());
+    assertArrayEquals(new String[] {"PermanentFailure"}, resolved.getDoNotRetry());
+  }
+
+  @MethodRetry(initialIntervalSeconds = 5, backoffCoefficient = 4.0, maximumAttempts = 10)
+  public void annotatedRetry() {}
 }