diff --git a/sentry_sdk/integrations/opentelemetry/potel_span_processor.py b/sentry_sdk/integrations/opentelemetry/potel_span_processor.py
index cddaf24ab2..ebb5bbc17a 100644
--- a/sentry_sdk/integrations/opentelemetry/potel_span_processor.py
+++ b/sentry_sdk/integrations/opentelemetry/potel_span_processor.py
@@ -7,7 +7,7 @@
 from sentry_sdk import capture_event
 from sentry_sdk.integrations.opentelemetry.utils import (
     is_sentry_span,
-    convert_otel_timestamp,
+    convert_from_otel_timestamp,
     extract_span_data,
 )
 from sentry_sdk.integrations.opentelemetry.consts import (
@@ -141,8 +141,8 @@ def _root_span_to_transaction_event(self, span):
             # TODO-neel-potel tx source based on integration
             "transaction_info": {"source": "custom"},
             "contexts": contexts,
-            "start_timestamp": convert_otel_timestamp(span.start_time),
-            "timestamp": convert_otel_timestamp(span.end_time),
+            "start_timestamp": convert_from_otel_timestamp(span.start_time),
+            "timestamp": convert_from_otel_timestamp(span.end_time),
         }  # type: Event
 
         return event
@@ -168,8 +168,8 @@ def _span_to_json(self, span):
             "op": op,
             "description": description,
             "status": status,
-            "start_timestamp": convert_otel_timestamp(span.start_time),
-            "timestamp": convert_otel_timestamp(span.end_time),
+            "start_timestamp": convert_from_otel_timestamp(span.start_time),
+            "timestamp": convert_from_otel_timestamp(span.end_time),
             "origin": origin or SPAN_ORIGIN,
         }  # type: dict[str, Any]
 
diff --git a/sentry_sdk/integrations/opentelemetry/utils.py b/sentry_sdk/integrations/opentelemetry/utils.py
index ecb1852404..2444131002 100644
--- a/sentry_sdk/integrations/opentelemetry/utils.py
+++ b/sentry_sdk/integrations/opentelemetry/utils.py
@@ -14,7 +14,7 @@
 from sentry_sdk._types import TYPE_CHECKING
 
 if TYPE_CHECKING:
-    from typing import Optional, Mapping, Sequence
+    from typing import Optional, Mapping, Sequence, Union
 
 
 GRPC_ERROR_MAP = {
@@ -72,11 +72,20 @@ def is_sentry_span(span):
     return False
 
 
-def convert_otel_timestamp(time):
+def convert_from_otel_timestamp(time):
     # type: (int) -> datetime
+    """Convert an OTel nanosecond-level timestamp to a datetime."""
     return datetime.fromtimestamp(time / 1e9, timezone.utc)
 
 
+def convert_to_otel_timestamp(time):
+    # type: (Union[datetime.datetime, float]) -> int
+    """Convert a datetime to an OTel timestamp (with nanosecond precision)."""
+    if isinstance(time, datetime):
+        return int(time.timestamp() * 1e9)
+    return int(time * 1e9)
+
+
 def extract_span_data(span):
     # type: (ReadableSpan) -> tuple[str, str, Optional[str], Optional[int], Optional[str]]
     op = span.name