They were outplayed in the opening half but improved after the break and grabbed all the points from two set piece moves.
Oxford went in front with their first attack of the game. Left back Matt Robinson fired over a long cross from the left and Craig Davies found space on the edge of the six-yard box to head into the top corner.
The goal capped an excellent week for the teenager who made his first appearance for the full Welsh International team when he came on as a midweek substitute against Slovenia.
Oxford had the game under control but lacked the power to finish.
They should have killed the game off four minutes after the break when Lee Bradbury broke through the Lincoln offside trap and was left with just keeper Alan Marriott to beat.
But Marriott forced him wide and he could only produce a weak cross which was easily cut out.
Lincoln got their equaliser in the 62nd minute when Gary Birch headed in a Paul Mayo free kick for his third goal in four games.
Lincoln substitute Marvin Robinson almost got on the score sheet 11 minutes later but was inches away from converting a Birch cross.
But Lincoln sealed the game in the 74th minute when the Oxford defence failed to clear a corner and Derek Asamoah blasted home.
Oxford had two late chances to equalise. But Davies shot wide from close in after a mistake by Lincoln's Jamie McCombe. Then skipper Chris Hargreaves saw his header bounce in front of goal and clear the bar.
Both teams finished up with 10 men after late dismissals saw both Mayo and Hargreaves red-carded after each picked up two bookings.