The Oklahoma City Thunder player, 28, beat out Pittsburgh Penguins captain Sidney Crosby, Chicago Cubs third baseman Kris Bryant and Olympic swimmer Michael Phelps.
In his acceptance speech, Westbrook thanked his wife, Nina Earl, and their son, Noah Russell, along with his NBA teammates.
In June, Westbrook beat out Kawhi Leonard and James Harden to win the NBA MVP trophy.
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The 25th annual ESPYS are broadcasting live on ABC Wednesday, July 12, at 8 p.m. ET from the Microsoft Theater in Los Angeles.