diff --git a/packager/packager.cc b/packager/packager.cc
index 953d1c8d25..5f9c400364 100644
--- a/packager/packager.cc
+++ b/packager/packager.cc
@@ -279,6 +279,8 @@ Status ValidateParams(const PackagingParams& packaging_params,
   // generates multiple segments specified using segment template.
   const bool on_demand_dash_profile =
       stream_descriptors.begin()->segment_template.empty();
+  std::set<std::string> outputs;
+  std::set<std::string> segment_templates;
   for (const auto& descriptor : stream_descriptors) {
     if (on_demand_dash_profile != descriptor.segment_template.empty()) {
       return Status(error::INVALID_ARGUMENT,
@@ -304,6 +306,27 @@ Status ValidateParams(const PackagingParams& packaging_params,
       // Skip the check for DASH as DASH defaults to 'dynamic' MPD when segment
       // template is provided.
     }
+
+    if (!descriptor.output.empty()) {
+      if (outputs.find(descriptor.output) != outputs.end()) {
+        return Status(
+            error::INVALID_ARGUMENT,
+            "Seeing duplicated outputs '" + descriptor.output +
+                "' in stream descriptors. Every output must be unique.");
+      }
+      outputs.insert(descriptor.output);
+    }
+    if (!descriptor.segment_template.empty()) {
+      if (segment_templates.find(descriptor.segment_template) !=
+          segment_templates.end()) {
+        return Status(error::INVALID_ARGUMENT,
+                      "Seeing duplicated segment templates '" +
+                          descriptor.segment_template +
+                          "' in stream descriptors. Every segment template "
+                          "must be unique.");
+      }
+      segment_templates.insert(descriptor.segment_template);
+    }
   }
 
   if (packaging_params.output_media_info && !on_demand_dash_profile) {
diff --git a/packager/packager_test.cc b/packager/packager_test.cc
index 9050388f8d..a776f239ca 100644
--- a/packager/packager_test.cc
+++ b/packager/packager_test.cc
@@ -10,6 +10,7 @@
 #include "packager/packager.h"
 
 using testing::_;
+using testing::HasSubstr;
 using testing::Invoke;
 using testing::MockFunction;
 using testing::Return;
@@ -25,6 +26,7 @@ const char kTestFile[] = "packager/media/test/data/bear-640x360.mp4";
 const char kOutputVideo[] = "output_video.mp4";
 const char kOutputVideoTemplate[] = "output_video_$Number$.m4s";
 const char kOutputAudio[] = "output_audio.mp4";
+const char kOutputAudioTemplate[] = "output_audio_$Number$.m4s";
 const char kOutputMpd[] = "output.mpd";
 
 const double kSegmentDurationInSeconds = 1.0;
@@ -138,6 +140,51 @@ TEST_F(PackagerTest, MixingSegmentTemplateAndSingleSegment) {
   ASSERT_EQ(error::INVALID_ARGUMENT, status.error_code());
 }
 
+TEST_F(PackagerTest, DuplicatedOutputs) {
+  std::vector<StreamDescriptor> stream_descriptors;
+  StreamDescriptor stream_descriptor;
+
+  stream_descriptor.input = kTestFile;
+  stream_descriptor.stream_selector = "video";
+  stream_descriptor.output = GetFullPath(kOutputVideo);
+  stream_descriptor.segment_template = GetFullPath(kOutputVideoTemplate);
+  stream_descriptors.push_back(stream_descriptor);
+
+  stream_descriptor.input = kTestFile;
+  stream_descriptor.stream_selector = "audio";
+  stream_descriptor.output = GetFullPath(kOutputVideo);
+  stream_descriptor.segment_template = GetFullPath(kOutputAudioTemplate);
+  stream_descriptors.push_back(stream_descriptor);
+
+  Packager packager;
+  auto status = packager.Initialize(SetupPackagingParams(), stream_descriptors);
+  ASSERT_EQ(error::INVALID_ARGUMENT, status.error_code());
+  EXPECT_THAT(status.error_message(), HasSubstr("duplicated outputs"));
+}
+
+TEST_F(PackagerTest, DuplicatedSegmentTemplates) {
+  std::vector<StreamDescriptor> stream_descriptors;
+  StreamDescriptor stream_descriptor;
+
+  stream_descriptor.input = kTestFile;
+  stream_descriptor.stream_selector = "video";
+  stream_descriptor.output = GetFullPath(kOutputVideo);
+  stream_descriptor.segment_template = GetFullPath(kOutputVideoTemplate);
+  stream_descriptors.push_back(stream_descriptor);
+
+  stream_descriptor.input = kTestFile;
+  stream_descriptor.stream_selector = "audio";
+  stream_descriptor.output = GetFullPath(kOutputAudio);
+  stream_descriptor.segment_template = GetFullPath(kOutputVideoTemplate);
+  stream_descriptors.push_back(stream_descriptor);
+
+  Packager packager;
+  auto status = packager.Initialize(SetupPackagingParams(), stream_descriptors);
+  ASSERT_EQ(error::INVALID_ARGUMENT, status.error_code());
+  EXPECT_THAT(status.error_message(),
+              HasSubstr("duplicated segment templates"));
+}
+
 TEST_F(PackagerTest, SegmentAlignedAndSubsegmentNotAligned) {
   auto packaging_params = SetupPackagingParams();
   packaging_params.chunking_params.segment_sap_aligned = true;