Jonny O'Mara mainly plays on the lower class tournaments of the Future and Challenger Tour. So far he has won a single and 16 double titles on the Future Tour. He celebrated his first success on the Challenger Tour in Izmir with his partner Scott Clayton . His opponent Denys Moltschanow and Serhij Stachowskyj had to cancel the final due to an injury Moltschanow, so that he won the double title without a fight .
In 2017 he came to his premiere in Eastbourne in doubles through a wildcard on the ATP World Tour . Together with Scott Clayton he lost the first round against Diego Schwartzman and Jiří Veselý . His Grand Slam debut was more successful. Also at the side of Scott Clayton, he benefited at Wimbledon from an injury-related abandonment of his opponents Paolo Lorenzi and Adrian Mannarino at the end of the second set. In the second round he was eliminated in three sets against the top seeded duo Henri Kontinen and John Peers . While he was once in the top 500 in singles, he achieved his best ranking in the world in doubles with 152nd place .