Back
Ben Arthurs' spectacular strike in the second period earned the Seasiders only their second league win of the season.
Goalkeeper Patrick Solis Grogan produced a couple of outstanding saves as Ballymena piled on the pressure in the closing stages but the Seasiders held on to claim victory.
They now leap-frog Portadown into 11th position in the table, while Ballymena drop into the bottom half.
Ballymena had an early opening when Kodi Lyons-Foster flicked on a long throw and James Hood got in behind to force keeper Patrick Solis Groggan to put the ball behind.
At the other end, Ben Arthurs ran into the left channel and shrugged off the challenge of Scot Whiteside but from his cross to the back post, Iestyn Hughes, at full stretch couldn't keep his header on target.
Ballymena threatened again with Lyons-Foster getting his head on a Charlie Allen free kick, forcing Solis Grogan to dive to his left to flick the ball behind.
Bangor struck the frame of the goal on the half-hour mark as Mackenzie Strachan's inswinging free kick eluded everyone in the middle and clipped the top of the crossbar on its way over.
The visitors continued to look threatening from set pieces with Tiarnan Mulvenna meeting another Strachan delivery with a glancing header, but it drifted wide of the far post.
Late in the half, Arthurs met a Reece Neale cross with a firm header which forced United keeper David Walsh to tip the ball over.
The visitors eventually broke the deadlock in spectacular fashion on 53 minutes when Mulvenna knocked the ball into the path of Arthurs who struck a first-time shot beyond Walsh into the top corner.
Bangor had goalkeeper Solis Grogan to thank for preserving their lead on 70 minutes when he produced a stunning save low to his right to keep out Chris McKee's effort.
Arthurs had another sight of the Ballymena goal, only to shoot tamely at Walsh.
At the other end, Solis Grogan made another important intervention to deflect Success Edogun's effort over the crossbar, while Chris McKee headed wide late on.