The 35-year-old lit up a dreary Saturday afternoon with some top draw touches as his Walsall side came from behind to maintain their impressive recent form.
The Bantams, who were without a win in ten games, got the start they wanted when striker Michael Branch fired them ahead after four minutes, but instead of being inspired they completely lost their way.
Winger Ben Muirhead was City's best attacking option and it was his early charge down the left-wing which set up Branch's strike.
Muirhead picked out skipper Dean Windass with the perfect cross and when he headed the ball down the unmarked Branch stroked the ball past James Walker from eight yards.
But with Merson pulling the strings Walsall responded with some neat football and it was only a matter of time before they levelled.
The Walsall play-maker curled a 24th-minute chance wide and midfielder Darren Wrack fizzed a 20-yard effort just over the bar.
The visitors got their reward after 34 minutes when Merson's classy dummy completely wrong footed the defence.
Full-back Chris Baird took full advantage to blast a fierce drive against the City bar and when the ball came back, Wrack drilled home the rebound from 10 yards. Five minutes later Merson picked out striker Gary Birch with a superb pass and Bradford keeper Alan Combe did brilliantly to tip his shot round the post.
Merson's influence faded in the second period as Bradford showed more urgency but they rarely looked like securing their second home win of the season.
The visitors had a penalty appeal waved away after Birch went tumbling as Combe raced of his line and the City stopper came to the rescue again when he blocked another close-range effort from the Saddlers front man ten minutes from time.
City, who were playing in front of their lowest league crowd of the season, had a strong penalty shout of their own turned down and midfielder Fraser McHugh came closest to snatching the winner with a well struck 30 yard volley.