diff --git a/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/EmbraceSpanImpl.kt b/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/EmbraceSpanImpl.kt
index 84b66584a..aca6c6495 100644
--- a/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/EmbraceSpanImpl.kt
+++ b/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/EmbraceSpanImpl.kt
@@ -56,7 +56,7 @@ internal class EmbraceSpanImpl(
             false
         } else {
             var successful: Boolean
-            val attemptedStartTimeMs = startTimeMs ?: openTelemetryClock.now().nanosToMillis()
+            val attemptedStartTimeMs = startTimeMs?.normalizeTimestampAsMillis() ?: openTelemetryClock.now().nanosToMillis()
             synchronized(startedSpan) {
                 startedSpan.set(spanBuilder.startSpan(attemptedStartTimeMs))
                 successful = startedSpan.get() != null
@@ -74,7 +74,7 @@ internal class EmbraceSpanImpl(
             false
         } else {
             var successful = false
-            val attemptedEndTimeMs = endTimeMs ?: openTelemetryClock.now().nanosToMillis()
+            val attemptedEndTimeMs = endTimeMs?.normalizeTimestampAsMillis() ?: openTelemetryClock.now().nanosToMillis()
 
             synchronized(startedSpan) {
                 startedSpan.get()?.let { spanToStop ->
diff --git a/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/EmbraceTracer.kt b/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/EmbraceTracer.kt
index 4a36fbcad..17a8fe053 100644
--- a/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/EmbraceTracer.kt
+++ b/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/EmbraceTracer.kt
@@ -22,7 +22,7 @@ internal class EmbraceTracer(
         spanService.startSpan(
             name = name,
             parent = parent,
-            startTimeMs = startTimeMs,
+            startTimeMs = startTimeMs?.normalizeTimestampAsMillis(),
             internal = false
         )
 
diff --git a/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/InternalTracer.kt b/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/InternalTracer.kt
index 0612bf6d2..bfc09a2e6 100644
--- a/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/InternalTracer.kt
+++ b/embrace-android-sdk/src/main/java/io/embrace/android/embracesdk/internal/spans/InternalTracer.kt
@@ -26,7 +26,10 @@ internal class InternalTracer(
     }
 
     override fun stopSpan(spanId: String, errorCode: ErrorCode?, endTimeMs: Long?): Boolean =
-        spanRepository.getSpan(spanId = spanId)?.stop(errorCode = errorCode, endTimeMs = endTimeMs) ?: false
+        spanRepository.getSpan(spanId = spanId)?.stop(
+            errorCode = errorCode,
+            endTimeMs = endTimeMs?.normalizeTimestampAsMillis()
+        ) ?: false
 
     override fun <T> recordSpan(
         name: String,
diff --git a/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/EmbraceSpanImplTest.kt b/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/EmbraceSpanImplTest.kt
index c64609555..eb1c3b9be 100644
--- a/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/EmbraceSpanImplTest.kt
+++ b/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/EmbraceSpanImplTest.kt
@@ -120,6 +120,22 @@ internal class EmbraceSpanImplTest {
         }
     }
 
+    @Test
+    fun `starting and stopping span with nanosecond timestamps`() {
+        with(embraceSpan) {
+            val expectedStartTimeMs = fakeClock.now() + 99
+            val expectedEndTimeMs = fakeClock.now() + 505
+            assertTrue(start(startTimeMs = expectedStartTimeMs.millisToNanos()))
+            assertTrue(stop(errorCode = ErrorCode.FAILURE, endTimeMs = expectedEndTimeMs.millisToNanos()))
+            assertSnapshot(
+                expectedStartTimeMs = expectedStartTimeMs,
+                expectedEndTimeMs = expectedEndTimeMs,
+                expectedStatus = Span.Status.ERROR
+            )
+            validateStoppedSpan()
+        }
+    }
+
     @Test
     fun `check adding events`() {
         with(embraceSpan) {
diff --git a/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/EmbraceTracerTest.kt b/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/EmbraceTracerTest.kt
index 59281a380..335f2b73f 100644
--- a/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/EmbraceTracerTest.kt
+++ b/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/EmbraceTracerTest.kt
@@ -81,8 +81,13 @@ internal class EmbraceTracerTest {
         val parent = checkNotNull(embraceTracer.startSpan(name = "test-span"))
         clock.tick(20L)
         val childStartTimeMs = clock.now() - 10L
-        val child =
-            checkNotNull(embraceTracer.startSpan(name = "child-span", parent = parent, startTimeMs = childStartTimeMs))
+        val child = checkNotNull(
+            embraceTracer.startSpan(
+                name = "child-span",
+                parent = parent,
+                startTimeMs = childStartTimeMs,
+            )
+        )
         assertTrue(parent.stop())
         assertTrue(child.stop())
         val spans = spanSink.flushSpans()
@@ -294,6 +299,26 @@ internal class EmbraceTracerTest {
         }
     }
 
+    @Test
+    fun `start and stop span with nanosecond timestamp`() {
+        spanSink.flushSpans()
+        val expectedStartTimeNanos = clock.nowInNanos()
+        val span = checkNotNull(
+            embraceTracer.startSpan(
+                name = "fallback-span",
+                parent = null,
+                startTimeMs = expectedStartTimeNanos
+            )
+        )
+        clock.tick(10L)
+        val expectedEndTimeNanos = clock.nowInNanos()
+        assertTrue(span.stop(endTimeMs = expectedEndTimeNanos))
+        with(verifyPublicSpan("fallback-span")) {
+            assertEquals(expectedStartTimeNanos, startTimeNanos)
+            assertEquals(expectedEndTimeNanos, endTimeNanos)
+        }
+    }
+
     @Test
     fun `recording completed spans fallback normalizes timestamps to millis when appropriate`() {
         val expectedName = "test-span"
diff --git a/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/InternalTracerTest.kt b/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/InternalTracerTest.kt
index 88914de39..1cf5f29b1 100644
--- a/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/InternalTracerTest.kt
+++ b/embrace-android-sdk/src/test/java/io/embrace/android/embracesdk/internal/spans/InternalTracerTest.kt
@@ -76,6 +76,20 @@ internal class InternalTracerTest {
         }
     }
 
+    @Test
+    fun `start and stop span with nanosecond timestamp`() {
+        spanSink.flushSpans()
+        val expectedStartTimeNanos = clock.nowInNanos()
+        val spanId = checkNotNull(internalTracer.startSpan(name = "my-span", startTimeMs = expectedStartTimeNanos))
+        clock.tick(10L)
+        val expectedEndTimeNanos = clock.nowInNanos()
+        assertTrue(internalTracer.stopSpan(spanId = spanId, endTimeMs = expectedEndTimeNanos))
+        with(verifyPublicSpan("my-span")) {
+            assertEquals(expectedStartTimeNanos, startTimeNanos)
+            assertEquals(expectedEndTimeNanos, endTimeNanos)
+        }
+    }
+
     @Test
     fun `verify event timestamp fallback`() {
         spanSink.flushSpans()