The Football Association has fined West Ham £115,000 for failing to control their fans at Upton Park after violence broke out at a Carling Cup tie against Millwall.
The Hammers, who have 14 days to appeal, were found guilty on two of four charges relating to the game last August and must also pay £5,000 costs.
Millwall were cleared of three charges while allegations both clubs failed to prevent racist behaviour were unproven.
Pitch invasions by West Ham fans followed each of their side’s goals in the 3-1 extra-time win.
Millwall had pleaded their innocence and vigorously defended the charges.
“We have always maintained that we were innocent of the charges,” said Lions chief executive officer Andy Ambler.
“As ever this club condemns all misbehaviour within football stadia and works tirelessly to eradicate misconduct and to continue to change an unfair and distorted misconception of Millwall Football Club and its fans.”
Eyewitness reports suggested fans threw bottles and bricks at each other as fights broke out outside the ground.
Inside the stadium, police and stewards battled to remove fans who had invaded the pitch from the home sections of the crowd.