The Stormers took full advantage of Josh Mann-Rea's red card to run in two late tries and secure a 31-11 Super Rugby victory against the Brumbies at Newlands.
The previously unbeaten Brumbies played the last 16 minutes with 14 men, after reserve hooker Mann-Rea was sent off for throwing punches at opposing front rower Oliver Kebble.
The Stormers scored three tries to one in the match played early Sunday (AEDT), though two of their five pointers came in the last five minutes.
The home team, who like the Brumbies now have a 3-1 record, did an excellent job of starving the visitors of possession in the Stormers' half.
Winger Henry Speight scored the Brumbies' only try in one of their rare forays into the Stormers' 22.
Speight beat both opposing wingers after taking a long cut-out pass from centre Tevita Kuridrani, who had made a defence-splitting run.
That try was the Brumbies' only score of the first half which ended with the Stormers holding a 9-5 advantage, courtesy of three penalties to five-eighth Kurt Coleman.
Brumbies fly-half Christian Lealiifano's first penalty cut the deficit to one early in the second half, but that blew out to eight after Coleman converted a try to flanker Siya Kolisi before Mann-Rea was dismissed.
Leali'ifano cut the gap to five with his second penalty, but that was the Brumbies' last score.
Stormers' winger Dillyn Leyds was awarded a try despite doubt over whether he had contact with the ball and their reserve forward Vincent Koch crashed over from close range right at the end.