diff --git a/api/BUILD.bazel b/api/BUILD.bazel
index 4c5e750b5e4..3d1543a0192 100644
--- a/api/BUILD.bazel
+++ b/api/BUILD.bazel
@@ -11,6 +11,7 @@ java_library(
     deps = [
         artifact("com.google.code.findbugs:jsr305"),
         artifact("com.google.errorprone:error_prone_annotations"),
+        artifact("org.jspecify:jspecify"),
         artifact("com.google.guava:failureaccess"),  # future transitive dep of Guava. See #5214
         artifact("com.google.guava:guava"),
     ],
diff --git a/api/build.gradle b/api/build.gradle
index 415a17f61f8..f4a254d3934 100644
--- a/api/build.gradle
+++ b/api/build.gradle
@@ -37,6 +37,7 @@ dependencies {
     compileOnly sourceSets.context.output
     api libraries.jsr305,
             libraries.errorprone.annotations
+            libraries.jspecify
     implementation libraries.guava
 
     testFixturesApi libraries.truth
diff --git a/api/src/main/java/io/grpc/StatusOr.java b/api/src/main/java/io/grpc/StatusOr.java
index 0f1e9da3c75..1850020a136 100644
--- a/api/src/main/java/io/grpc/StatusOr.java
+++ b/api/src/main/java/io/grpc/StatusOr.java
@@ -22,25 +22,27 @@
 import com.google.common.base.MoreObjects;
 import com.google.common.base.MoreObjects.ToStringHelper;
 import com.google.common.base.Objects;
-import javax.annotation.Nullable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 /** Either a Status or a value. */
 @ExperimentalApi("https://github.com/grpc/grpc-java/issues/11563")
-public class StatusOr<T> {
-  private StatusOr(Status status, T value) {
+@NullMarked
+public class StatusOr<T extends @Nullable Object> {
+  private StatusOr(@Nullable Status status, @Nullable T value) {
+    assert status == null || value == null : "is `status` is not `null` then `value` should be `null`";
     this.status = status;
     this.value = value;
   }
 
   /** Construct from a value. */
-  public static <T> StatusOr<T> fromValue(@Nullable T value) {
-    StatusOr<T> result = new StatusOr<T>(null, value);
-    return result;
+  public static <T extends @Nullable Object> StatusOr<T> fromValue(T value) {
+    return new StatusOr<>(null, value);
   }
 
   /** Construct from a non-Ok status. */
-  public static <T> StatusOr<T> fromStatus(Status status) {
-    StatusOr<T> result = new StatusOr<T>(checkNotNull(status, "status"), null);
+  public static <T extends @Nullable Object> StatusOr<T> fromStatus(Status status) {
+    StatusOr<T> result = new StatusOr<>(checkNotNull(status, "status"), null);
     checkArgument(!status.isOk(), "cannot use OK status: %s", status);
     return result;
   }
@@ -54,7 +56,7 @@ public boolean hasValue() {
    * Returns the value if set or throws exception if there is no value set. This method is meant
    * to be called after checking the return value of hasValue() first.
    */
-  public @Nullable T getValue() {
+  public T getValue() {
     if (status != null) {
       throw new IllegalStateException("No value present.");
     }
@@ -105,6 +107,6 @@ public String toString() {
     return stringHelper.toString();
   }
 
-  private final Status status;
-  private final T value;
+  private final @Nullable Status status;
+  private final @Nullable T value;
 }
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index cb5dce02843..075909a818d 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -34,6 +34,7 @@ cronet-embedded = "org.chromium.net:cronet-embedded:119.6045.31"
 errorprone-annotations = "com.google.errorprone:error_prone_annotations:2.36.0"
 # error-prone 2.32.0+ require Java 17+
 errorprone-core = "com.google.errorprone:error_prone_core:2.31.0"
+jspecify = "org.jspecify:jspecify:1.0.0"
 google-api-protos = "com.google.api.grpc:proto-google-common-protos:2.59.2"
 # google-auth-library 1.25.0+ requires error_prone_annotations 2.31.0+, which
 # breaks the Android build