The Somalia-born Briton, champion over 5,000m and 10,000m at both last year’s London Olympics and this year’s World Championships, made the revelation in his new autobiography, which is being serialised in British newspaper the Daily Telegraph.
Farah said that the incident happened on Christmas Day in 2009 after he asked a couple with a pram not to block a path in Richmond Park in southwest London.
Farah said: “All of a sudden the man stepped towards me, as if he wanted to fight. He was much taller and bigger than me, but I did not want to back down. We were in each other’s faces.
Then it all kicked off. Before I knew it, we were having a full-blown fight, rolling around on the ground, trading blows. Onlookers had to pull us apart before things got really bad.”