Kuznetsov skated the puck along the top of the zone, faked a pass to Ovechkin and then charged the net from the left side. He went untouched to below the left circle and beat Al Montoya stick side.
The Capitals have won two in a row and seven of their past eight.
Washington goaltender Philipp Grubauer made 26 saves. Montoya had 25 for Florida.