diff --git a/modules/audio_mixer/BUILD.gn b/modules/audio_mixer/BUILD.gn
index fe20f3d6c7..fb038bf677 100644
--- a/modules/audio_mixer/BUILD.gn
+++ b/modules/audio_mixer/BUILD.gn
@@ -122,6 +122,7 @@ if (rtc_include_tests) {
       "../../rtc_base:checks",
       "../../rtc_base:stringutils",
       "../../rtc_base:task_queue_for_test",
+      "../../system_wrappers:metrics",
       "../../test:test_support",
     ]
   }
diff --git a/modules/audio_mixer/audio_mixer_impl.cc b/modules/audio_mixer/audio_mixer_impl.cc
index 0c203a1d9f..666497484b 100644
--- a/modules/audio_mixer/audio_mixer_impl.cc
+++ b/modules/audio_mixer/audio_mixer_impl.cc
@@ -22,6 +22,7 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/trace_event.h"
+#include "system_wrappers/include/metrics.h"
 
 namespace webrtc {
 
@@ -186,6 +187,7 @@ bool AudioMixerImpl::AddSource(Source* audio_source) {
       << "Source already added to mixer";
   audio_source_list_.emplace_back(new SourceStatus(audio_source, false, 0));
   helper_containers_->resize(audio_source_list_.size());
+  UpdateSourceCountStats();
   return true;
 }
 
@@ -263,4 +265,14 @@ bool AudioMixerImpl::GetAudioSourceMixabilityStatusForTest(
   RTC_LOG(LS_ERROR) << "Audio source unknown";
   return false;
 }
+
+void AudioMixerImpl::UpdateSourceCountStats() {
+  size_t current_source_count = audio_source_list_.size();
+  // Log to the histogram whenever the maximum number of sources increases.
+  if (current_source_count > max_source_count_ever_) {
+    RTC_HISTOGRAM_COUNTS_LINEAR("WebRTC.Audio.AudioMixer.NewHighestSourceCount",
+                                current_source_count, 1, 20, 20);
+    max_source_count_ever_ = current_source_count;
+  }
+}
 }  // namespace webrtc
diff --git a/modules/audio_mixer/audio_mixer_impl.h b/modules/audio_mixer/audio_mixer_impl.h
index 76b1131777..e1040defd7 100644
--- a/modules/audio_mixer/audio_mixer_impl.h
+++ b/modules/audio_mixer/audio_mixer_impl.h
@@ -71,6 +71,8 @@ class AudioMixerImpl : public AudioMixer {
  private:
   struct HelperContainers;
 
+  void UpdateSourceCountStats() RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+
   // Compute what audio sources to mix from audio_source_list_. Ramp
   // in and out. Update mixed status. Mixes up to
   // kMaximumAmountOfMixedAudioSources audio sources.
@@ -94,6 +96,9 @@ class AudioMixerImpl : public AudioMixer {
 
   // Component that handles actual adding of audio frames.
   FrameCombiner frame_combiner_;
+
+  // The highest source count this mixer has ever had. Used for UMA stats.
+  size_t max_source_count_ever_ = 0;
 };
 }  // namespace webrtc
 
diff --git a/modules/audio_mixer/audio_mixer_impl_unittest.cc b/modules/audio_mixer/audio_mixer_impl_unittest.cc
index e4b12a7000..8022332b27 100644
--- a/modules/audio_mixer/audio_mixer_impl_unittest.cc
+++ b/modules/audio_mixer/audio_mixer_impl_unittest.cc
@@ -28,6 +28,7 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/strings/string_builder.h"
 #include "rtc_base/task_queue_for_test.h"
+#include "system_wrappers/include/metrics.h"
 #include "test/gmock.h"
 #include "test/gtest.h"
 
@@ -42,6 +43,8 @@ namespace webrtc {
 namespace {
 
 constexpr int kDefaultSampleRateHz = 48000;
+const char kSourceCountHistogramName[] =
+    "WebRTC.Audio.AudioMixer.NewHighestSourceCount";
 
 // Utility function that resets the frame member variables with
 // sensible defaults.
@@ -214,6 +217,41 @@ TEST(AudioMixer, LargestEnergyVadActiveMixed) {
   }
 }
 
+TEST(AudioMixer, UpdatesSourceCountHistogram) {
+  constexpr int kAudioSourcesGroup1 = 5;
+  constexpr int kAudioSourcesGroup2 = 3;
+
+  const auto mixer = AudioMixerImpl::Create();
+
+  MockMixerAudioSource participants[kAudioSourcesGroup1 + kAudioSourcesGroup2];
+
+  // Add the sources in group 1.
+  for (int i = 0; i < kAudioSourcesGroup1; ++i) {
+    EXPECT_TRUE(mixer->AddSource(&participants[i]));
+    EXPECT_EQ(i + 1, metrics::NumSamples(kSourceCountHistogramName));
+    EXPECT_EQ(1, metrics::NumEvents(kSourceCountHistogramName, i + 1));
+  }
+  // Remove the sources again.
+  for (int i = 0; i < kAudioSourcesGroup1; ++i) {
+    mixer->RemoveSource(&participants[i]);
+  }
+  // Add the first group again. This should not add anything new to the
+  // histogram.
+  for (int i = 0; i < kAudioSourcesGroup1; ++i) {
+    EXPECT_TRUE(mixer->AddSource(&participants[i]));
+    EXPECT_EQ(kAudioSourcesGroup1,
+              metrics::NumSamples(kSourceCountHistogramName));
+    EXPECT_EQ(1, metrics::NumEvents(kSourceCountHistogramName, i + 1));
+  }
+  // Add the second group. This adds to the histogram again.
+  for (int i = kAudioSourcesGroup1;
+       i < kAudioSourcesGroup1 + kAudioSourcesGroup2; ++i) {
+    EXPECT_TRUE(mixer->AddSource(&participants[i]));
+    EXPECT_EQ(i + 1, metrics::NumSamples(kSourceCountHistogramName));
+    EXPECT_EQ(1, metrics::NumEvents(kSourceCountHistogramName, i + 1));
+  }
+}
+
 TEST(AudioMixer, FrameNotModifiedForSingleParticipant) {
   const auto mixer = AudioMixerImpl::Create();