Capital One Cup semi-finalists Bradford suffered a setback in the race for promotion from League Two.
Bradford are in the semi-final of the League Cup on Tuesday night when they welcome Premier League side Aston Villa to what will be a packed Valley Parade for the first leg.
But in the bread and butter of the league they stuttered to a defeat in North London on Saturday.
Barnet took the lead just minutes before the half-time break with a goal from Taiwo Atieno.
John Oster doubled the Barnet lead three minutes after the restart to pile the agony onto the Bantams.
Manager Phil Parkinson said: “We wanted to go into (Tuesday) with a win, but it wasn’t meant to be.
“We’ve worked very hard to get to this stage and we’re going to enjoy it.
“We totally dominated [Barnet] didn’t we? We had 21 attempts on goal and to not score is very unusual, we conceded two goals at bad times which gave them a lift.”