The Bees went a goal behind after only six minutes of the League Two clash when Dany N’Guessan converted a cross from Scott Kerr. But Brentford were quick to hit back and midfielder Marcus Bean levelled in the 13th minute when he broke down the middle and finished with a low shot.
The Bees inched in front nine minutes later when Dean Bowditch smashed home a first-time shot from inside the box.
Lincoln were reduced to 10 men in the 38th minute when defender Paul Green was shown a straight red card for a two-footed challenge on Brentford skipper Kevin O’Connor.
Brentford then missed the easiest of chances to extend their lead when Bowditch set up MacDonald, but with an empty net in front of him the striker somehow fired over the crossbar from two yards.
And Lincoln made Brentford pay after 66 minutes when veteran striker Geoff Horsfield, making his comeback after treatment for cancer, headed the ball on for Anthony Elding to equalise.