South Yorkshire Police confirmed it was looking into the claim that an unnamed player abused the ball boy during the League One club's 1-1 draw against Sheffield United at Bramall Lane.
The Greater Manchester side said the player denied the allegation and that they and his team-mates were fully supportive of him.
In a statement last night, the club said: "Oldham Athletic Football Club was made aware by South Yorkshire Police after today's npower League One match at Sheffield United of an allegation of racist abuse by one of its players.
"The player has categorically denied the allegation and the club and his team-mates are fully supportive of him.
"The club understands that the police are making enquiries into the allegation and, as a result, will not be making any further statements in relation to this matter."