diff --git a/src/base/allocator/partition_allocator/src/partition_alloc/partition_root.cc b/src/base/allocator/partition_allocator/src/partition_alloc/partition_root.cc
index 57a278891c..06db42602d 100644
--- a/src/base/allocator/partition_allocator/src/partition_alloc/partition_root.cc
+++ b/src/base/allocator/partition_allocator/src/partition_alloc/partition_root.cc
@@ -282,7 +282,12 @@ void PartitionAllocMallocInitOnce() {
     return;
   }
 
-#if PA_BUILDFLAG(IS_LINUX) || PA_BUILDFLAG(IS_CHROMEOS)
+#if defined(__MUSL__)
+  // Musl calls malloc() in pthread_atfork(), resulting in a deadlock.
+  static_cast<void>(BeforeForkInParent);
+  static_cast<void>(AfterForkInParent);
+  static_cast<void>(AfterForkInChild);
+#elif PA_BUILDFLAG(IS_LINUX) || PA_BUILDFLAG(IS_CHROMEOS)
   // When fork() is called, only the current thread continues to execute in the
   // child process. If the lock is held, but *not* by this thread when fork() is
   // called, we have a deadlock.
diff --git a/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_default_dispatch_to_partition_alloc.cc b/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_default_dispatch_to_partition_alloc.cc
index e576dc3ee6..f4a5bb9efd 100644
--- a/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_default_dispatch_to_partition_alloc.cc
+++ b/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_default_dispatch_to_partition_alloc.cc
@@ -660,7 +660,9 @@ SHIM_ALWAYS_EXPORT int mallopt(int cmd, int value) __THROW {
 
 #endif  // !PA_BUILDFLAG(IS_APPLE) && !PA_BUILDFLAG(IS_ANDROID)
 
-#if PA_BUILDFLAG(IS_LINUX) || PA_BUILDFLAG(IS_CHROMEOS)
+#if defined(__MUSL__) 
+// Musl does not support struct mallinfo.
+#elif PA_BUILDFLAG(IS_LINUX) || PA_BUILDFLAG(IS_CHROMEOS)
 SHIM_ALWAYS_EXPORT struct mallinfo mallinfo(void) __THROW {
   partition_alloc::SimplePartitionStatsDumper allocator_dumper;
   Allocator()->DumpStats("malloc", true, &allocator_dumper);
diff --git a/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_internals.h b/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_internals.h
index afa815114a..d7d178d646 100644
--- a/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_internals.h
+++ b/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_internals.h
@@ -9,7 +9,9 @@
 
 #if defined(__GNUC__)
 
-#if PA_BUILDFLAG(IS_POSIX)
+#if defined(__MUSL__)
+// Musl does not provide sys/cdefs.h
+#elif PA_BUILDFLAG(IS_POSIX)
 #include <sys/cdefs.h>  // for __THROW
 #endif
 
diff --git a/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_override_libc_symbols.h b/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_override_libc_symbols.h
index 0bc286ef95..76925ebb11 100644
--- a/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_override_libc_symbols.h
+++ b/src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_override_libc_symbols.h
@@ -25,6 +25,12 @@
 
 #include "partition_alloc/shim/allocator_shim_internals.h"
 
+// Musl does not specify anything for malloc() etc.
+#if defined(__MUSL__)
+#undef __THROW
+#define __THROW
+#endif
+
 extern "C" {
 
 // WARNING: Whenever a new function is added there (which, surprisingly enough,