The on-loan Aston Villa midfielder was charged following an incident involving Aberdeen defender Shay Logan during a Scottish Premiership match last month.
The Bulgarian was ordered to appear before the SFA's judicial panel, which ruled he had committed "excessive misconduct by the use of offensive, insulting and abusive language of a racist nature".
However, Celtic insist they are backing their player's claims of innocence and plan to appeal.
A club spokesperson said: "Racism has no place in football and as a club for all people, Celtic absolutely abhors racism of any kind.
"This was a very unfortunate case, but the club has accepted Aleksandar's explanation that he did not say the words that were alleged to have been said and that he is not a racist.
"We are, therefore, very disappointed by the outcome today and can confirm that Aleksandar will be appealing this decision."
Source : PA
Source: PA