He was walking on the Lagan Towpath in Lisburn around 3.30 pm on Saturday.
Three males shouted racist abuse at him, then punched him several times in the head.
The man, who is black, got away and ran to a bar in Bridge Street.
A 16-year-old boy and two men, aged 18 and 22, were arrested a short time later.
The victim was taken to hospital for treatment to injuries that are not believed to be life-threatening.