Substitute Andrew Proctor struck a late winner as Accrington ended Barnet's run of five straight home wins.
The Bees had the better of the first period but Stanley stole a lead through Andy Todd's penalty after Ian Hendon pushed Robbie Williams in the back.
Barnet were level at half-time thanks to Adam Birchall tap-in.
But after sub Liam Hatch was sent off 11 minutes from time, Proctor popped up to grab an 84th-minute winner and Barnet then had Barry Cogan sent off.
Barnet: Burch, Hendon, Yakubu, King, Gross (Allen 89), Cogan, Bailey, Hessenthaler (Lewis 89), Graham, Birchall, Puncheon (Hatch 57).
Subs Not Used: Warhurst, Nicolau.
Sent Off: Hatch (79), Cogan (90).
Booked: Hendon, Cogan, Birchall.
Goals: Birchall 45.
Accrington Stanley: Kazimierczak, Rogers, Almeida, Williams, Edwards, Boco (Whalley 78), Harris (Proctor 52), Grant, Todd, Mullin, Fleetwood (Mangan 63).
Subs Not Used: Welch, Richardson. Booked: Williams, Rogers, Almeida.
Goals: Todd 40 pen, Proctor 84. Att: 2,041
Ref: D Whitestone (Northamptonshire).