diff --git a/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp b/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp
--- a/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp
@@ -88,6 +88,8 @@
       Result.Nodes.getNodeAs<CXXConversionDecl>("conversion")) {
     if (Conversion->isOutOfLine())
       return;
+    if (Conversion->getExplicitSpecifier().isSpecified())
+      return;
     SourceLocation Loc = Conversion->getLocation();
     // Ignore all macros until we learn to ignore specific ones (e.g. used in
     // gmock to define matchers).
@@ -133,7 +135,7 @@
   }
 
   if (Ctor->isExplicit() || Ctor->isCopyOrMoveConstructor() ||
-      TakesInitializerList)
+      TakesInitializerList || Ctor->getExplicitSpecifier().isSpecified())
     return;
 
   bool SingleArgument =
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -156,6 +156,10 @@
 - Removed default setting ``cppcoreguidelines-explicit-virtual-functions.IgnoreDestructors = "true"``,
   to match the current state of the C++ Core Guidelines.
 
+- Updated :doc:`google-explicit-constructor
+  <clang-tidy/checks/google-explicit-constructor>` check to ignore constructors
+  or conversion operators where they are marked ``explicit(false)``.
+
 - Updated :doc:`google-readability-casting
   <clang-tidy/checks/google-readability-casting>` to diagnose and fix functional
   casts, to achieve feature parity with the corresponding ``cpplint.py`` check.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/google-explicit-constructor-cxx20.cpp b/clang-tools-extra/test/clang-tidy/checkers/google-explicit-constructor-cxx20.cpp
new file mode 100644
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/google-explicit-constructor-cxx20.cpp
@@ -0,0 +1,17 @@
+// RUN: %check_clang_tidy -std=c++20 %s google-explicit-constructor %t
+
+struct Foo {
+  Foo(int) {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: single-argument constructors must be marked explicit to avoid unintentional implicit conversions
+  // CHECK-FIXES: {{^}}  explicit Foo(int) {}
+  explicit Foo(long) {}
+  explicit(false) Foo(float) {}
+  explicit(true) Foo(double) {}
+
+  operator int() const;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: 'operator int' must be marked explicit to avoid unintentional implicit conversions
+  // CHECK-FIXES: {{^}}  explicit operator int() const;
+  explicit operator long() const;
+  explicit(false) operator float() const;
+  explicit(true) operator double() const;
+};