The 31-year-old, who was also "severely warned" as to his future conduct, had been charged following an exchange with a Tottenham supporter after West Ham's 2-2 draw at White Hart Lane.
Cole has well over 100,000 Twitter followers and was responding to a message from the Spurs supporter Stuart Hardy that said: "Hi @CarltonCole1 when your own team-mates don't kick the ball out when you're lying injured for 2 mins, you think it's time to call it a day?", Cole replied: "F off you c***" before later deleting the tweet.
But he was charged by the FA, which confirmed he had been fined with a short statement on its website.
"Following an Independent Regulatory Commission hearing today, Carlton Cole has been fined £20,000 after he admitted breaching FA Rules in relation to social media," it read.
"The West Ham United player, who was also severely warned as to his future conduct, admitted posting a comment on his Twitter account which was abusive and/or insulting and/or improper and/or brought the game into disrepute, in breach of FA Rule E3."
Cole, who is currently recovering from a hamstring injury that forced him off during the game at Tottenham, will look at Rio Ferdinand as an example of how to avoid future misdeameanours.
The QPR defender was handed a three-game ban earlier this season for a second FA charge over social media activities - with the former England captain not contesting the suspension despite labelling the severity of the decision as 'crazy'.
Source : PA
Source: PA