The Portland Timbers shot-stopper was named on Thursday evening as the winner after beating Vancouver Whitecaps goalkeeper David Ousted.
Click here to watch the save.
Outsted’s point-blank reaction save on striker Andrew Wenger on 9 May in Vancouver was considered to be among the finest saves and was among the 32 nominees for the award.
But Kwarasey's save and Outsted's effort were left in the final shortlist with the Ghanaian emerging as the winner in the poll determined by an online fan vote.
The Portland Timbers gloves man was awarded for his leaping, fingertip save on a well-struck shot from behind the box.
Real Salt Lake midfielder Luke Mulholland hit a piledriver from outside the box in their clash with Timbers on 15 August in Utah which forced Kwarasey to dive to his right to save with one hand.
With the score tied 0-0 in the 31st minute, Mulholland delivered an unstoppable one-time volley from long range that Kwarasey was able to get his fingertips on to push the ball wide of the upper, left corner.
Portland went on to tally the game-winning goal on the road in the final minute of second-half stoppage time for a 1-0 win.
Portland will face the Columbus Crew SC for the MLS Cup Sunday.