Barritt's try and the subsequent Owen Farrell touchline conversion put Saracens ahead for the only time in the match and the result kept the reigning champions in second place in the table.
The match, which saw the return to club action of Mike Tindall and Eliota Fuimaono-Sapolu after their respective World Cup controversies, was niggly throughout after a fracas inside 15 seconds lit the blue touch paper and referee Tim Wigglesworth had to talk to both captains.
The first scoring chance fell to Gloucester when they broke into the visiting 22 but full-back Olly Morgan threw a high pass to the right which was out of wing Charlie Sharples' reach.
Referee Wigglesworth was called into disciplinary action again on 14 minutes when Sarries centre Farrell went in high on opposite number Henry Trinder.
After calling Farrell and captain Steve Borthwick over to him, he let the Saracen off with a warning, but Cherry and Whites fly-half Freddie Burns exacted punishment by kicking the three points.
Saracens twice lost control of the ball when in attacking positions and harmed their cause further by conceding penalties to allow Gloucester to clear their lines.
And ex-England full-back Morgan stretched the hosts' lead with a superb try when he linked with Trinder to run 40 metres to the line, though Burns missed the conversion to follow an earlier wasted penalty chance.
Saracens broke their duck when fly-half Charlie Hodgson booted a 40-metre penalty but within minutes, Burns added a second penalty to put the home side 11-3 in front at the break.
But Saracens turned the tables in the second half as Farrell landed two penalties to put them back in the match.
Rival looseheads Nick Wood, of the home side, and Rhys Gill were sent to the sin-bin after trading punches - and further Saracens mistakes allowed Burns' replacement Tim Taylor to kick two penalties and take Gloucester 17-9 ahead.
Still, however, there was little between the sides as Saracens pressed for the try that would get them back into the match.
Farrell put them within losing bonus point range with his third penalty and bravely, when they were awarded a kickable penalty with five minutes left, Sarries went for the driving line-out option.
And it paid off as Farrell put a grubber kick behind the home defence, Barritt caught it and, after a video referee verdict because scrum-half Rory Lawson was underneath the ball, the try was given.
Farrell's conversion put Sarries in the lead and there was nothing Gloucester could do to avoid defeat.
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