Ballymena claimed the scalp of Bruff, who are always a formidable prospect at Kilballyowen Park, as John Andrews’ side moved up to fifth in the Division 1B table.
This was a superbly entertaining game in which Bruff had led 15-14 coming up to half-time, and they were still 25-24 ahead in the 69th minute.
Replacement John Semple helped Ballymena turn the screw in the closing minutes, scampering over for a converted try and kicking a final penalty for a deserved 34-28 win.
The Braidmen went in front thanks to a converted try from South African centre Richard Aingworth, who was scoring for the second week running, but Bruff were back level thanks to a seven-pointer from player-coach Peter Malone.
Ulster prospect Blane McIlroy then broke through for Ballymena’s second try, however the hosts hit the front thanks to a Mark Cosgrave touchdown and a Brian Cahill penalty.
But even though replacement John Carroll added a third Bruff try into the second half and Cahill finished with 13 points, the Ulster outfit were just too strong.
Ballymena, who were missing the injured Luke Marshall and Mike McComish, started briskly in what was their first ever trip to Kilballyowen Park.
A missed penalty was followed by the opening try. The visitors won a turnover following a good tackle by flanker Paul Pritchard and recent signing Aingworth broke through for a fifth minute try which David O'Hara converted.
Bruff used their powerful forwards to gain ground. Brian Cahill missed his first shot at the posts and a knock on spoilt a promising move. Back they came, this time Malone rumbling over from close range with Cahill's conversion levelling the sides.
Cahill landed the first of two more penalty opportunities, but Ballymena soon had their second converted try on the board. Scrum half McIlroy sidestepped past Eoghan Maher for the score.
Bruff then edged back in front courtesy of a try in the corner from winger Cosgrave, but John Andrews' men had the final say before half-time. They kicked a penalty to the corner and won another one which O'Hara sent over for a 17-15 advantage.
There was no more scoring until the 55th minute when Aingworth broke through a couple of tackles to score his third try in two league games. O'Hara's conversion put nine points between the sides.
Shortly afterwards, Semple kicked ahead and in the chase Aingworth steamed past and as his hat-trick looked certain, he gave the last touch marginally too much and the ball beat him over the end line.
On the hour mark, a piece of Ballymena RFC history was made with the introduction of the 18-year-old John Andrew, joining his brothers Joel and Ricky on the pitch. It marked the first time that three brothers have played together in a league game for the club.
Suddenly though, Bruff were right back in the hunt. Cahill converted a penalty and then added the extras to Carroll's touchdown, making it 25-24 to Malone's charges.
Both sides gave it their all in the final quarter. Just when it looked like Bruff might strike again, Semple brilliantly intercepted a pass to run the length of the pitch and score Ballymena's bonus point try which he converted himself.
Semple got the Braidmen over the finish line with an injury-time penalty. Cahill cancelled that kick out to seal a late losing bonus point for Bruff, but Ballymena were left to celebrate their second triumph on Munster soil in the space of three weeks.
Referee: John Carvill (IRFU)