Jason Puncheon struck on the stroke of half-time as Barnet fought back from a goal down to put the skids under 10-man Bristol Rovers' play-off chances.
Bees hitman Adam Birchall almost opened the scoring after 10 minutes when his shot was well saved by Steve Phillips.
And it proved a valuable stop as Richard Walker lost his marker to head home his 18th of the season for Rovers.
However, Puncheon's 25-yard free-kick drew Barnet level before Aaron Lescott saw red for a foul on Dean Sinclair.
Barnet: Flitney, Ioannou (Allen 76), King, Devera, Nicolau, Cogan, Bailey, Sinclair, Puncheon, Hatch, Birchall.
Subs Not Used: Harrison, Grazioli, Graham, Vieira.
Booked: Sinclair, Hatch.
Goals: Puncheon 45.
Bristol Rovers: Phillips, Lescott, Hinton (Igoe 75), Elliott, Carruthers, Haldane (Anthony 51), Campbell, Disley, Jacobson, Lambert, Walker (Nicholson 69).
Subs Not Used: Sandell, Lines.
Sent Off: Lescott (48).
Goals: Walker 12.
Att: 2,541.
Ref: R Shoebridge (Derbyshire).