diff --git a/lib/libc/amd64/string/strcat.S b/lib/libc/amd64/string/strcat.S
--- a/lib/libc/amd64/string/strcat.S
+++ b/lib/libc/amd64/string/strcat.S
@@ -1,6 +1,14 @@
-/*
- * Written by J.T. Conklin <jtc@acorntoolworks.com>
- * Public domain.
+/*-
+ * Copyright (c) 2023, The FreeBSD Foundation
+ *
+ * SPDX-License-Expression: BSD-2-Clause
+ *
+ * Portions of this software were developed by Robert Clausecker
+ * <fuz@FreeBSD.org> under sponsorship from the FreeBSD Foundation.
+ *
+ * Adapted from NetBSD's common/lib/libc/arch/x86_64/string/strcat.S
+ * written by J.T. Conklin <jtc@acorntoolworks.com>
+ * that was originally dedicated to the public domain
  */
 
 #include <machine/asm.h>
@@ -8,7 +16,14 @@
 	RCSID("$NetBSD: strcat.S,v 1.4 2004/07/26 18:51:21 drochner Exp $")
 #endif
 
-ENTRY(strcat)
+#include "amd64_archlevel.h"
+
+ARCHFUNCS(strcat)
+	ARCHFUNC(strcat, scalar)
+	ARCHFUNC(strcat, baseline)
+ENDARCHFUNCS(strcat)
+
+ARCHENTRY(strcat, scalar)
 	movq	%rdi,%rax
 	movabsq	$0x0101010101010101,%r8
 	movabsq	$0x8080808080808080,%r9
@@ -161,6 +176,28 @@
 
 .Ldone:
 	ret
-END(strcat)
+ARCHEND(strcat, scalar)
+
+/*
+ * Call into strlen + strcpy if we have any SIMD at all.
+ * The scalar implementation above is better for the scalar
+ * case as it avoids the function call overhead, but pessimal
+ * if we could call SIMD routines instead.
+ */
+ARCHENTRY(strcat, baseline)
+	push	%rbp
+	mov	%rsp, %rbp
+	push	%rsi
+	push	%rbx
+	mov	%rdi, %rbx		# remember destination for later
+	call	CNAME(strlen)		# strlen(dest)
+	mov	-8(%rbp), %rsi
+	lea	(%rbx, %rax, 1), %rdi	# dest + strlen(dest)
+	call	CNAME(__stpcpy)		# stpcpy(dest + strlen(dest), src)
+	mov	%rbx, %rax		# return dest
+	pop	%rbx
+	leave
+	ret
+ARCHEND(strcat, baseline)
 
 	.section .note.GNU-stack,"",%progbits
diff --git a/share/man/man7/simd.7 b/share/man/man7/simd.7
--- a/share/man/man7/simd.7
+++ b/share/man/man7/simd.7
@@ -24,7 +24,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE
 .
-.Dd November 9, 2023
+.Dd November 14, 2023
 .Dt SIMD 7
 .Os
 .Sh NAME
@@ -66,7 +66,7 @@
 .It    rindex            Ta    S       Ta        Ta    S1     Ta    S
 .It    stpcpy            Ta            Ta        Ta    S1
 .It    stpncpy           Ta            Ta        Ta    S1
-.It    strcat            Ta            Ta        Ta    S      Ta    S
+.It    strcat            Ta            Ta        Ta    S1     Ta    S
 .It    strchr            Ta    S       Ta        Ta    S1     Ta    S
 .It    strchrnul         Ta            Ta        Ta    S1
 .It    strcmp            Ta            Ta    S   Ta    S1     Ta    S