According to the news agency AP, Forlán, 45, enters the doubles tournament in Uruguay Open, a Challenger tournament on the ATP tour.
Forlán plays alongside Argentine Federico Coria on the clay court in Montevideo.
Forlán, who has regularly played tennis in lower-level competitions for some time, says he was inspired by his father Pablo, who also started playing tennis after his football career.
He started playing tennis when he was 41. That's also why I've been playing since I was two years old, says the former football striker.
Diego Forlán played for Manchester United, Atlético Madrid, Inter and Penarol.
He was one of the most prominent players when Uruguay reached the semifinal in the World Championship in South Africa in 2010 and a year later lifted the trophy in Copa America.