diff --git a/share/man/man8/beinstall.8 b/share/man/man8/beinstall.8
--- a/share/man/man8/beinstall.8
+++ b/share/man/man8/beinstall.8
@@ -41,10 +41,8 @@
 also automatically performs
 .Pa /etc
 updates
-(using either
-.Xr etcupdate 8
-or
-.Xr mergemaster 8 )
+(using
+.Xr etcupdate 8 )
 and
 package updates using
 .Xr pkg-upgrade 8
@@ -88,18 +86,12 @@
 .It Ev CONFIG_UPDATER Pq default: Dq Li "etcupdate"
 Config updater:
 .Xr etcupdate 8
-and
-.Xr mergemaster 8
-are supported.
+is supported.
 Set to an empty string to skip.
 .It Ev ETCUPDATE_FLAGS Pq default: Dq Li "-F"
 Flags for
 .Xr etcupdate 8
 if used.
-.It Ev MERGEMASTER_FLAGS Pq default: Dq Li "-iFU"
-Flags for
-.Xr mergemaster 8
-if used.
 .It Ev NO_PKG_UPGRADE Pq default: Dq Li ""
 If not empty,
 .Dq Li pkg upgrade
@@ -117,7 +109,6 @@
 .Xr development 7 ,
 .Xr bectl 8 ,
 .Xr etcupdate 8 ,
-.Xr mergemaster 8 ,
 .Xr pkg 8
 .Sh HISTORY
 .Nm
diff --git a/tools/build/beinstall.sh b/tools/build/beinstall.sh
--- a/tools/build/beinstall.sh
+++ b/tools/build/beinstall.sh
@@ -45,13 +45,10 @@
 BE_UTILITY="${BE_UTILITY:-"bectl"}"
 # If not empty, 'pkg upgrade' will be skipped.
 NO_PKG_UPGRADE="${NO_PKG_UPGRADE:-""}"
-# Config updater - 'etcupdate' and 'mergemaster' are supported.  Set to an
-# empty string to skip.
+# Config updater - 'etcupdate' is supported.  Set to an empty string to skip.
 CONFIG_UPDATER="${CONFIG_UPDATER:-"etcupdate"}"
 # Flags for etcupdate if used.
 ETCUPDATE_FLAGS="${ETCUPDATE_FLAGS:-"-F"}"
-# Flags for mergemaster if used.
-MERGEMASTER_FLAGS="${MERGEMASTER_FLAGS:-"-iFU"}"
 
 
 ########################################################################
@@ -122,14 +119,6 @@
 	return 0
 }
 
-update_mergemaster_pre() {
-	${MERGEMASTER_CMD} -p -m ${srcdir} -D ${BE_MNTPT} -t ${BE_MM_ROOT} ${MERGEMASTER_FLAGS}
-}
-
-update_mergemaster() {
-	${MERGEMASTER_CMD} -m ${srcdir} -D ${BE_MNTPT} -t ${BE_MM_ROOT} ${MERGEMASTER_FLAGS}
-}
-
 update_etcupdate_pre() {
 	${ETCUPDATE_CMD} -p -s ${srcdir} -D ${BE_MNTPT} ${ETCUPDATE_FLAGS} || return $?
 	${ETCUPDATE_CMD} resolve -D ${BE_MNTPT} || return $?
@@ -176,7 +165,6 @@
 
 ## Constants
 ETCUPDATE_CMD="${srcdir}/usr.sbin/etcupdate/etcupdate.sh"
-MERGEMASTER_CMD="${srcdir}/usr.sbin/mergemaster/mergemaster.sh"
 
 # May be a worktree, in which case .git is a file, not a directory.
 if [ -e .git ] ; then
@@ -206,7 +194,6 @@
 [ $? -ne 0 -o ! -d ${BE_TMP} ] && errx "Unable to create mountpoint"
 [ -z "$NO_CLEANUP_BE" ] && cleanup_commands="rmdir_be ${cleanup_commands}"
 BE_MNTPT=${BE_TMP}/mnt
-BE_MM_ROOT=${BE_TMP}/mergemaster # mergemaster will create
 mkdir -p ${BE_MNTPT}
 
 ${BE_UTILITY} create ${BENAME} >/dev/null || errx "Unable to create BE ${BENAME}"