diff --git a/docs/changelog/114177.yaml b/docs/changelog/114177.yaml
new file mode 100644
index 000000000000..d68486469d79
--- /dev/null
+++ b/docs/changelog/114177.yaml
@@ -0,0 +1,5 @@
+pr: 114177
+summary: "Make `randomInstantBetween` always return value in range [minInstant, `maxInstant]`"
+area: Infra/Metrics
+type: bug
+issues: []
diff --git a/test/framework/src/main/java/org/elasticsearch/test/ESTestCase.java b/test/framework/src/main/java/org/elasticsearch/test/ESTestCase.java
index 068a666d78d7..31c8e5bc3d45 100644
--- a/test/framework/src/main/java/org/elasticsearch/test/ESTestCase.java
+++ b/test/framework/src/main/java/org/elasticsearch/test/ESTestCase.java
@@ -900,10 +900,11 @@ public abstract class ESTestCase extends LuceneTestCase {
      * @return a random instant between a min and a max value with a random nanosecond precision
      */
     public static Instant randomInstantBetween(Instant minInstant, Instant maxInstant) {
-        return Instant.ofEpochSecond(
-            randomLongBetween(minInstant.getEpochSecond(), maxInstant.getEpochSecond()),
-            randomLongBetween(0, 999999999)
-        );
+        long epochSecond = randomLongBetween(minInstant.getEpochSecond(), maxInstant.getEpochSecond());
+        long minNanos = epochSecond == minInstant.getEpochSecond() ? minInstant.getNano() : 0;
+        long maxNanos = epochSecond == maxInstant.getEpochSecond() ? maxInstant.getNano() : 999999999;
+        long nanos = randomLongBetween(minNanos, maxNanos);
+        return Instant.ofEpochSecond(epochSecond, nanos);
     }
 
     /**