Defender Michael Nottingham produced a great finish 20 minutes from time to earn Accrington a 2-1 triumph at Oxford.
Nottingham controlled a clearance with a fine first touch then hammered in a half-volley from 10 yards to bring Stanley a vital win for their faint hopes of reaching the play-offs, and all but ending Oxford's.
Accrington thought they should have had a goal when Dion Charles looked to have stabbed the ball over the line at a corner, but it was not given.
However, John Coleman's men went in front from their next attack, on 16 minutes, when on-loan QPR forward Paul Smyth fired high into the net from 15 yards.
Oxford equalised nine minutes later with Elliot Lee slotting home from Matt Taylor's pass.
Jack Stevens' smart double save kept the U's level as he turned Sean McConville's free-kick onto a post then smartly saved a follow-up shot.
At the other end Toby Savin saved well from Lee and Olamide Shodipo before Nottingham popped up with the winner.