Duquesne played a great first half and led Richmond by 15 points on the road Saturday night.
The Dukes then fell apart in the second half, but still had a chance to win after Tevin Brewer's go-ahead jumper with 21 seconds left.
The Spiders made the big shot when they needed it, though, burying a 3-pointer with 7 seconds to go for a 75-73 win in Richmond.
Duquesne was looking to move to 3-1 in the Atlantic 10 and appeared to be in good shape after a dominant first half led to a 49-34 lead.