diff --git a/sbin/sysctl/Makefile b/sbin/sysctl/Makefile
--- a/sbin/sysctl/Makefile
+++ b/sbin/sysctl/Makefile
@@ -6,6 +6,11 @@
 WARNS?=	3
 MAN=	sysctl.8
 
+.if ${MK_JAIL} != "no" && !defined(RESCUE)
+CFLAGS+= -DJAIL
+LIBADD+= jail
+.endif
+
 HAS_TESTS=
 SUBDIR.${MK_TESTS}+=	tests
 
diff --git a/sbin/sysctl/sysctl.8 b/sbin/sysctl/sysctl.8
--- a/sbin/sysctl/sysctl.8
+++ b/sbin/sysctl/sysctl.8
@@ -36,12 +36,14 @@
 .Nd get or set kernel state
 .Sh SYNOPSIS
 .Nm
+.Op Fl j Ar jail
 .Op Fl bdeFhiJlNnoqTtVWx
 .Op Fl B Ar bufsize
 .Op Fl f Ar filename
 .Ar name Ns Op = Ns Ar value Ns Op , Ns Ar value
 .Ar ...
 .Nm
+.Op Fl j Ar jail
 .Op Fl bdeFhJlNnoqTtVWx
 .Op Fl B Ar bufsize
 .Fl a
@@ -113,6 +115,10 @@
 are necessarily running exactly the same software) easier.
 .It Fl J
 Display only jail prision sysctl variables (CTLFLAG_PRISON).
+.It Fl j Ar jail
+Perform the actions inside the
+.Ar jail
+(by jail id or jail name).
 .It Fl l
 Show the length of variables along with their values.
 This option cannot be combined with the
diff --git a/sbin/sysctl/sysctl.c b/sbin/sysctl/sysctl.c
--- a/sbin/sysctl/sysctl.c
+++ b/sbin/sysctl/sysctl.c
@@ -33,6 +33,9 @@
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
+#ifdef JAIL
+#include <sys/jail.h>
+#endif
 #include <sys/sysctl.h>
 #include <sys/vmmeter.h>
 #include <dev/evdev/input.h>
@@ -51,6 +54,9 @@
 #include <err.h>
 #include <errno.h>
 #include <inttypes.h>
+#ifdef JAIL
+#include <jail.h>
+#endif
 #include <locale.h>
 #include <stdbool.h>
 #include <stdio.h>
@@ -121,8 +127,8 @@
 {
 
 	(void)fprintf(stderr, "%s\n%s\n",
-	    "usage: sysctl [-bdeFhiJlNnoqTtVWx] [ -B <bufsize> ] [-f filename] name[=value] ...",
-	    "       sysctl [-bdeFhJlNnoqTtVWx] [ -B <bufsize> ] -a");
+	    "usage: sysctl [-j jail] [-bdeFhiJlNnoqTtVWx] [ -B <bufsize> ] [-f filename] name[=value] ...",
+	    "       sysctl [-j jail] [-bdeFhJlNnoqTtVWx] [ -B <bufsize> ] -a");
 	exit(1);
 }
 
@@ -131,12 +137,15 @@
 {
 	int ch;
 	int warncount = 0;
+#ifdef JAIL
+	int jid;
+#endif
 
 	setlocale(LC_NUMERIC, "");
 	setbuf(stdout,0);
 	setbuf(stderr,0);
 
-	while ((ch = getopt(argc, argv, "AaB:bdeFf:hiJlNnoqTtVWwXx")) != -1) {
+	while ((ch = getopt(argc, argv, "AaB:bdeFf:hiJj:lNnoqTtVWwXx")) != -1) {
 		switch (ch) {
 		case 'A':
 			/* compatibility */
@@ -172,6 +181,19 @@
 		case 'J':
 			Jflag = true;
 			break;
+		case 'j':
+#ifdef JAIL
+			if (optarg == NULL)
+				usage();
+			jid = jail_getid(optarg);
+			if (jid == -1)
+				errx(1, "jail not found");
+			if (jail_attach(jid) != 0)
+				errx(1, "cannot attach to jail");
+#else
+			errx(1, "not built with jail support");
+#endif
+			break;
 		case 'l':
 			lflag = true;
 			break;