diff --git a/changelog/3867.fixed.md b/changelog/3867.fixed.md
new file mode 100644
index 000000000..41ee584a2
--- /dev/null
+++ b/changelog/3867.fixed.md
@@ -0,0 +1 @@
+- Fixed `PipelineTask` double-inserting `RTVIProcessor` into the frame chain when the user provides both an `RTVIProcessor` in the pipeline and a custom `RTVIObserver` subclass in observers.
diff --git a/src/pipecat/pipeline/task.py b/src/pipecat/pipeline/task.py
index 2cfe26606..1db23e7d4 100644
--- a/src/pipecat/pipeline/task.py
+++ b/src/pipecat/pipeline/task.py
@@ -330,6 +330,7 @@ class PipelineTask(BasePipelineTask):
 
         # RTVI support
         self._rtvi = None
+        self._rtvi_external = False
         external_rtvi = self._find_processor(pipeline, RTVIProcessor)
         external_observer_found = any(isinstance(o, RTVIObserver) for o in observers)
 
@@ -349,6 +350,7 @@ class PipelineTask(BasePipelineTask):
                 "They are both added by default, no need to add them yourself."
             )
             self._rtvi = external_rtvi
+            self._rtvi_external = True
         elif enable_rtvi:
             self._rtvi = rtvi_processor or RTVIProcessor()
             observers.append(self._rtvi.create_rtvi_observer(params=rtvi_observer_params))
@@ -388,7 +390,13 @@ class PipelineTask(BasePipelineTask):
         # allows us to receive and react to downstream frames.
         source = PipelineSource(self._source_push_frame, name=f"{self}::Source")
         sink = PipelineSink(self._sink_push_frame, name=f"{self}::Sink")
-        processors = [self._rtvi, pipeline] if self._rtvi else [pipeline]
+        # Only prepend the RTVIProcessor if we created it ourselves. When the
+        # user already placed it inside their pipeline we must not insert it
+        # again or it will appear twice in the frame chain.
+        if self._rtvi and not self._rtvi_external:
+            processors = [self._rtvi, pipeline]
+        else:
+            processors = [pipeline]
         self._pipeline = Pipeline(processors, source=source, sink=sink)
 
         # The task observer acts as a proxy to the provided observers. This way,