The Bantams take the win on penalties to move into the semi-finals of the Capital One Cup, with three Gunners players missing their spot kicks and two hitting the woodwork
The Bantams took the lead after just 15 minutes thanks to Garry Thompson’s superb volley and both teams created further chances but were unable to take advantage of them.
Their defence almost managed to keep their Premier League opponents at bay throughout the second half, but Vermaelen scored in the 87th minute to force extra time.
Extra time remained goalless and penalties were required to separate the two teams, with Bradford prevailing thanks to three misses from their illustrious opponents.
The home side selected their strongest possible team for this fourth round tie, with Gary Jones captaining the Bantams, who currently sit fourth in the League Two table.
Meanwhile, Arsene Wenger selected a strong side, with Jack Wilshere handed a start in the midfield and Gervinho leading the line up front.
The home side took the lead in the 15th minute with their first real chance, as after a free kick caused havoc in the Arsenal box, Thompson volleyed home to give them an early advantage.
Bradford had the momentum after taking a surprise lead, while the away side struggled to penetrate their opponents’ defence.
However, the home side came close to an equaliser in the 37th minute, as after some superb trickery, Francis Coquelin struck an early shot against the post that bounced away to safety.
Gervinho then could not get on the end of a fizzing cross from yards out, before Bradford almost scored a late second as Nahki Wells sent a shot just wide after a James Hanson knock-down.
The Bantams’ confidence was clear and they went into the half-time break ahead after a superb opening period against an out-of-sorts Arsenal outfit.
It took until the 55th minute for either side to test their opponents’ defence once again, but Bradford were able to snuff out a long ball played towards Gervinho that the forward struggled to get under control.
It took until the 70th minute for the Gunners to create another real chance of note as they had their first effort on target through a long-range strike from substitute Alex Oxlade-Chamberlain.
The Gunners finally found their shooting boots in the 87th minute, though, with their equaliser coming from an unlikely source, courtesy of club captain Vermaelen heading home from a corner to draw his side level.
The game then went into extra time, with the best chance falling to Santi Cazorla, who hit the bar early in the second period.
However, with neither side able to find another goal, a penalty shootout was left to decide which team would go through to the semi-finals.
In the shootout, Arsenal hit the woodwork twice while the home side just about held their nerve to take the win and go through to the semis in what represents a humiliating giant-killing for the visitors and will only serve to increase the pressure on under-fire manager Arsene Wenger.