The Jamaica international now faces a three-match ban, meaning he will miss this Saturday's trip to Watford, next season's Championship opener and the first round of the Capital One Cup.
United striker El-Hadji Diouf will miss two games after his red card in the Brighton fixture.
Austin has made 38 appearances for Leeds, scoring four goals in his debut season in England after joining the club in the summer from Norwegian side Brann Bergen.
Source: LeedsUtdMAD
Source: FOOTYMAD