Liam Hatch's late winner for Barnet dented Darlington's play-off hopes on a miserable afternoon for the visitors.
The Quakers were up against it when Tommy Wright was sent off after just 55 seconds for elbowing Simon King.
Dean Sinclair cashed in to put Barnet ahead two minutes later, only for Darlington to level through David Wheater's header.
Hatch secured the points for Barnet after losing his marker and prodding home Nicky Bailey's free-kick.
Barnet: Harrison, Bailey, King (Warhurst 46), Gross (Hendon 86), Hatch, Sinclair, Yakubu, Devera, Nicolau, Cogan, Birchall (Grazioli 90).
Subs Not Used: Flitney, Allen. Booked: Devera.
Goals: Sinclair 4, Hatch 52.
Darlington: Russell, Phillips, Wainwright, Blundell (Armstrong 78), Smith (Prendergast 77), Wiseman, Rowson, Wright, Horwood (Joachim 67), Wheater, Ravenhill.
Subs Not Used: Stockdale, Collins.
Sent Off: Wright (2). Booked: Phillips, Smith, Ravenhill.
Goals: Wheater 22.
Att: 2,364.
Ref: R Lee (Essex).