Former Barbados international forward McCammon, 33, was sacked for alleged misconduct by the Kent club last summer.
McCammon told a court in Ashford that he and other black players at the club were treated differently from their white team-mates.
He said that he was refused private treatment at the club's expense for an operation while another white player was flown out to Dubai for treatment, and he was fined two weeks' wages after visiting a private consultant himself.
The 33-year-old also spoke of how he was ordered to drive to the ground in "treacherous" snowy conditions when some white players were allowed to stay away and how he was told not to post blogs online when others were permitted to do so.
In a club statement Gillingham, who finished eighth in League Two last season, said they were "hugely disappointed, in fact staggered" at the decision and are considering an appeal.
The statement read: "Today we have received the decision of the Ashford Employment Tribunal which sets out their findings that Mark McCammon was unfairly dismissed and that his dismissal was an act of racial victimisation.
"We are hugely disappointed, in fact staggered, by this decision. As an organisation we are an equal opportunity employer and do not discriminate against, nor victimise our staff.
"This case is the first of its kind to be brought against the club in its entire history, a history that has seen the club employ many thousands of staff of various race, religion and creed, none of whom have ever felt the need to bring such a claim.
"Given the nature of the case, and the findings, we will discuss the judgment with our lawyers and decide upon the next course of action, whether that be an appeal against the findings, or another form of action, as deemed appropriate. There will be no further comment on the case by the club until the matter has run its full course."