 Mokuna was originally talent-spotted by Sporting Lisbon which visited Léopoldville in 1954 during a tour of neighbouring Portuguese Angola.He moved to Portugal to play for Sporting from January 1955 and finished the season with 19 goals in 11 games.However, he remained with the team for only two seasons after being "ostracised" before returning to the Congo to play for AS Vita Club at Léopoldville.