diff --git a/api/legacy_stats_types.cc b/api/legacy_stats_types.cc
index e3b2144edd..278ac81a6e 100644
--- a/api/legacy_stats_types.cc
+++ b/api/legacy_stats_types.cc
@@ -12,6 +12,8 @@
 
 #include <string.h>
 
+#include <utility>
+
 #include "absl/algorithm/container.h"
 #include "api/make_ref_counted.h"
 #include "rtc_base/checks.h"
@@ -783,28 +785,28 @@ const StatsReport::Value* StatsReport::FindValue(StatsValueName name) const {
 StatsCollection::StatsCollection() {}
 
 StatsCollection::~StatsCollection() {
-  RTC_DCHECK(thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&thread_checker_);
   for (auto* r : list_)
     delete r;
 }
 
 StatsCollection::const_iterator StatsCollection::begin() const {
-  RTC_DCHECK(thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&thread_checker_);
   return list_.begin();
 }
 
 StatsCollection::const_iterator StatsCollection::end() const {
-  RTC_DCHECK(thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&thread_checker_);
   return list_.end();
 }
 
 size_t StatsCollection::size() const {
-  RTC_DCHECK(thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&thread_checker_);
   return list_.size();
 }
 
 StatsReport* StatsCollection::InsertNew(const StatsReport::Id& id) {
-  RTC_DCHECK(thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&thread_checker_);
   RTC_DCHECK(Find(id) == nullptr);
   StatsReport* report = new StatsReport(id);
   list_.push_back(report);
@@ -812,13 +814,13 @@ StatsReport* StatsCollection::InsertNew(const StatsReport::Id& id) {
 }
 
 StatsReport* StatsCollection::FindOrAddNew(const StatsReport::Id& id) {
-  RTC_DCHECK(thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&thread_checker_);
   StatsReport* ret = Find(id);
   return ret ? ret : InsertNew(id);
 }
 
 StatsReport* StatsCollection::ReplaceOrAddNew(const StatsReport::Id& id) {
-  RTC_DCHECK(thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&thread_checker_);
   RTC_DCHECK(id.get());
   Container::iterator it = absl::c_find_if(
       list_,
@@ -832,10 +834,37 @@ StatsReport* StatsCollection::ReplaceOrAddNew(const StatsReport::Id& id) {
   return InsertNew(id);
 }
 
+StatsCollection::Container StatsCollection::DetachCollection() {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+#if RTC_DCHECK_IS_ON
+  for (auto* report : list_)
+    report->DetachSequenceCheckers();
+#endif
+  return std::move(list_);
+}
+
+void StatsCollection::MergeCollection(Container collection) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+  for (auto* report : collection) {
+#if RTC_DCHECK_IS_ON
+    report->AttachSequenceCheckers();
+#endif
+    Container::iterator it = absl::c_find_if(list_, [&](const StatsReport* r) {
+      return r->id()->Equals(report->id());
+    });
+    if (it == list_.end()) {
+      list_.push_back(report);
+    } else {
+      delete *it;
+      *it = report;
+    }
+  }
+}
+
 // Looks for a report with the given `id`.  If one is not found, null
 // will be returned.
 StatsReport* StatsCollection::Find(const StatsReport::Id& id) {
-  RTC_DCHECK(thread_checker_.IsCurrent());
+  RTC_DCHECK_RUN_ON(&thread_checker_);
   Container::iterator it = absl::c_find_if(
       list_,
       [&id](const StatsReport* r) -> bool { return r->id()->Equals(id); });
diff --git a/api/legacy_stats_types.h b/api/legacy_stats_types.h
index a62e014834..e49cb6d6dd 100644
--- a/api/legacy_stats_types.h
+++ b/api/legacy_stats_types.h
@@ -344,8 +344,15 @@ class RTC_EXPORT StatsReport {
     // TODO(tommi): Move `name` and `display_name` out of the Value struct.
     const StatsValueName name;
 
+   protected:
+#if RTC_DCHECK_IS_ON
+    friend class StatsReport;
+    void DetachSequenceChecker() { thread_checker_.Detach(); }
+    void AttachSequenceChecker() { RTC_DCHECK_RUN_ON(&thread_checker_); }
+#endif
+
    private:
-    webrtc::SequenceChecker thread_checker_;
+    webrtc::SequenceChecker thread_checker_{webrtc::SequenceChecker::kDetached};
     mutable int ref_count_ RTC_GUARDED_BY(thread_checker_) = 0;
 
     const Type type_;
@@ -403,6 +410,19 @@ class RTC_EXPORT StatsReport {
 
   const Value* FindValue(StatsValueName name) const;
 
+#if RTC_DCHECK_IS_ON
+  void DetachSequenceCheckers() {
+    for (auto& v : values_) {
+      v.second->DetachSequenceChecker();
+    }
+  }
+  void AttachSequenceCheckers() {
+    for (auto& v : values_) {
+      v.second->AttachSequenceChecker();
+    }
+  }
+#endif
+
  private:
   // The unique identifier for this object.
   // This is used as a key for this report in ordered containers,
@@ -441,13 +461,16 @@ class StatsCollection {
   StatsReport* FindOrAddNew(const StatsReport::Id& id);
   StatsReport* ReplaceOrAddNew(const StatsReport::Id& id);
 
+  Container DetachCollection();
+  void MergeCollection(Container collection);
+
   // Looks for a report with the given `id`.  If one is not found, null
   // will be returned.
   StatsReport* Find(const StatsReport::Id& id);
 
  private:
   Container list_;
-  webrtc::SequenceChecker thread_checker_;
+  webrtc::SequenceChecker thread_checker_{SequenceChecker::kDetached};
 };
 
 }  // namespace webrtc
diff --git a/pc/legacy_stats_collector_unittest.cc b/pc/legacy_stats_collector_unittest.cc
index 6d3fd9f462..5e472a5c8d 100644
--- a/pc/legacy_stats_collector_unittest.cc
+++ b/pc/legacy_stats_collector_unittest.cc
@@ -40,6 +40,7 @@
 #include "rtc_base/fake_ssl_identity.h"
 #include "rtc_base/message_digest.h"
 #include "rtc_base/net_helper.h"
+#include "rtc_base/null_socket_server.h"
 #include "rtc_base/rtc_certificate.h"
 #include "rtc_base/socket_address.h"
 #include "rtc_base/ssl_identity.h"
@@ -846,6 +847,58 @@ class StatsCollectorTrackTest : public LegacyStatsCollectorTest,
   rtc::scoped_refptr<FakeAudioTrack> audio_track_;
 };
 
+TEST(StatsCollectionTest, DetachAndMerge) {
+  StatsCollection collection;
+  ASSERT_EQ(collection.size(), 0u);
+
+  // Create a new report with some information.
+  StatsReport::Id id(
+      StatsReport::NewTypedId(StatsReport::kStatsReportTypeTrack, "track_id"));
+  StatsReport* report = collection.ReplaceOrAddNew(id);
+  report->AddString(StatsReport::kStatsValueNameTrackId, "track_id");
+  ASSERT_TRUE(report);
+  // Check that looking it up, yields the same report.
+  ASSERT_EQ(report, collection.FindOrAddNew(id));
+  // There should be one report now.
+  ASSERT_EQ(collection.size(), 1u);
+
+  // Detach the internal container from the StatsCollection.
+  StatsCollection::Container container = collection.DetachCollection();
+  EXPECT_EQ(container.size(), 1u);
+  EXPECT_EQ(collection.size(), 0u);
+  EXPECT_EQ(nullptr, collection.Find(id));
+
+  // Merge it back and test if we find the same report.
+  collection.MergeCollection(std::move(container));
+  EXPECT_EQ(collection.size(), 1u);
+  EXPECT_EQ(report, collection.Find(id));
+}
+
+// Similar to `DetachAndMerge` above but detaches on one thread, merges on
+// another to test that we don't trigger sequence checker.
+TEST(StatsCollectionTest, DetachAndMergeThreaded) {
+  rtc::Thread new_thread(std::make_unique<rtc::NullSocketServer>());
+  new_thread.Start();
+
+  StatsReport::Id id(
+      StatsReport::NewTypedId(StatsReport::kStatsReportTypeTrack, "track_id"));
+
+  StatsReport* expected_report = nullptr;
+
+  StatsCollection::Container container = new_thread.BlockingCall([&] {
+    StatsCollection collection;
+    expected_report = collection.ReplaceOrAddNew(id);
+    expected_report->AddString(StatsReport::kStatsValueNameTrackId, "track_id");
+    return collection.DetachCollection();
+  });
+
+  StatsCollection collection;
+  collection.MergeCollection(std::move(container));
+  EXPECT_EQ(collection.size(), 1u);
+  EXPECT_EQ(expected_report, collection.Find(id));
+
+  new_thread.Stop();
+}
 TEST_F(LegacyStatsCollectorTest, FilterOutNegativeDataChannelId) {
   auto pc = CreatePeerConnection();
   auto stats = CreateStatsCollector(pc.get());