David Cushley was the toast of the home side as he netted the only goal of a pulsating game 12 minutes before the break to book their place in the last four.
The Braidmen entered the contest on the back of Saturday’s humiliating derby demolition at the hands of Coleraine.
Boss Glenn Ferguson demanded a positive reaction and United set about defending an unbeaten home record which now stretches all the way back to February – when Cliftonville were the victors.
It was the home side who were quickly out of the blocks and lively wideman Cushley notched up a trio of opportunities.
With six minutes on the clock he flashed a shot just wide of Ryan Brown’s far post, and a minute later tried his luck again – this time from distance – but saw his shot go the wrong side of the opposite post.
Midway through the half Cushley was on the end of Ross Black’s pinpoint cross from the left but headed the wrong side of the crossbar.
Cushley wasn’t to be denied the opener as he found the net with 33 minutes on the clock.
It came with James McCabe racing to the byline and his pass found Cushley who unleashed an unstoppable effort from the edge of the penalty area.
Six minutes before the break Aaron Stewart diverted a dangerous Martin Donnelly cross behind for a corner.
From the resulting set-piece sturdy defender Marc Smyth headed just wide to leave Ballymena with the interval advantage.
The first real opportunity of the second half came when Cushley turned provider for his former Distillery team mate Gary Thompson.
His inviting cross was just ahead of midfielder Thompson who was unable to get on the end of it and provided what looked a certain goal.
United continued to go in search of a second goal and were to spurn an even easier opportunity on 55 minutes, when McCabe somehow managed to miss from a header with the goal at his mercy.
Midway through the half Tommy Breslin introduced former Northern Ireland and Werder Bremen striker into the action in an attempt to summon an equaliser.
It almost paid dividends as his goal-bound effort produced a last ditch clearance from Johnny Taylor.
Ballymena: Nelson, Rodgers, Black, Taylor, Ruddy, Stuart, Thompson, Taggart, J Davidson (Lowry), McCabe (Surgenor), Cushley. Unused Subs: Teggart, Vauls, Munster.
Cliftonville: Brown, McGovern, Caldwell, McMullan, Garrett, Donnelly, O’Carroll, (Boyce) Seydak, Smyth, Catney, Cosgrove (Gormley). Unused Subs: Holland, Stuart, O’Kane.
Referee: Ross Dunlop (Carrickfergus)