A first half strike from Bradford born Clayton Donaldson was cancelled out by James Hanson's second goal in as many games as Phil Parkinson's men more than matched their League 1 opponents.
City made all the early groundwork in the opening stages of the game and Garry Thompson was brought down twice in quick succession just outside the area as he looked to build an attack. The first delivery from Nathan Doyle was cleared away but the second was a direct attempt at goal from Alan Connell that dipped a years or so ver the bar.
Brentford almost had an early lead in bizarre fashion; Clayton Donaldson's cross into the area struck Newcastle loanee Curtis Good and looped towards goal but Matt Duke was taking no chance and tipped the ball over the bar.
Much talked about young talent Harry Forrester then tried to stamp his own authority on the game by surging forward from midfield, he galloped forward unchallenged and hit a stinging shot towards goal that Duke had to react to; the shot was struck well enough but Matt Duke got everything behind the effort.
Against the run of general play somewhat, Brentford took the lead. A hopeful through ball wasn't dealt with by debutant Curtis Good and Donaldson clinically slotted the ball into the bottom corner without batting an eye lid to put the Londoners in front.
Early into the second half Donaldson almost doubled his tally for the evening; Sam Saunders' corner was headed powerfully by the former Crewe Alexandra front man but fortunately for The Bantams it flew inches wide of the post.
Matt Duke pulled off the best save of the game to deny Donaldson who was at the centre of all Brentford chances. Turning away brilliantly from his marker his goal bound shot from close range was beaten away by the inspired Duke.
Knowing a goal was needed very soon, Phil Parkinson made a triple substitution replacing Alan Connell, Garry Thompson and Ricky Ravenhill with Nahki Wells, Will Atkinson and Gary Jones respectively.
The change almost paid dividends straight away as Hanson knocked down into the Wells who forced Richard Lee into a smart save.
Six minutes later, The Bantams were back on level terms; James Meredith's cross caused chaos in the area as a couple of black shirts failed to clear the delivery, young loanee Blair Turgott tried to collect the loose ball and it rolled away unattended but Hanson duly obliged by calmly slotting a first time shot into the bottom corner.
A minute later City were almost at it again; a through ball found Wells but the ball was prodded away from him and Gary Jones steamed onto it to fire a powerful shot just over the bar from 20 yards.
Nahki Wells should've won it late on when he got between last defender Tony Craig and Bees' keeper Richard Lee to prod a shot through the latter's legs that came back off the post; neither Wells or any other nearby City players could get to the rebound and the ball was cleared to safety.
Wells' chance was the last of note during the tie as the game headed to a replay to ultimately decide which of the two teams would take their place in the 3rd Round of the FA Cup.