The Wizards became the 13th team in NBA history to lose its first 10 games of the season and extended the worst start to a campaign in franchise history.
Devan Harris forced overtime by hitting two free throws for Atlanta with 4 seconds left in regulation and the Wizards then suffered additional frustration at the end of the extra period.
Not only did Korver hit his critical shot at game's end for Atlanta, but Washington then missed a chance to win by a split second.
Washington called a time out after Korver's basket and Washington's Kevin Seraphin managed to get off a shot.
That attempt bounced off the rim, but Martell Webster grabbed the rebound for the Wizards and all in one motion put the ball back through the basket. A study of the television replay, however, showed the ball left Webster's hand after the lights surrounding the backboard came on -- indicating time had run out and negating the field goal.
Atlanta won its third straight game with Josh Smith scoring 25 points and Korver adding 16.
Seraphin produced 21 points and had 10 rebounds for the Wizards, who suffered 20 turnovers to 13 for Atlanta.