[1][3][4] He represented Australia at the 2012 Summer Paralympics in the men's singles and doubles wheelchair tennis events.

[3][7] Kellerman was selected to represent Australia at the 2012 Summer Paralympics in London, United Kingdom, in the men's singles and the doubles event where he teamed up with Ben Weekes.

[15] In July 2017 Kellerman was part of a humanitarian trip to Tanzania with one of his sponsors EG Funds to visit one of the charities they support Neema Crafts.

Kellerman shared his story and message of "to look for your abilities and strengths beyond any physical disability" with the staff of the Neema Crafts.

He also took this opportunity to run a training camp and donate equipment to the wheelchair tennis teams in Tanzania and Kenya.

[16][17] In Tanzania, Kellerman met former NSW parliamentarian Tony Stewart who had arranged an amazing welcome and tour at the orphanage he has supported for many years.

Tony Stewart challenged Kellerman to walk the Kokoda Track to raise money for Youth Off The Streets in collaboration with Clubs NSW as sponsor.

In October 2018 Kellerman, with business partner and friend Rani Vincent walked the Kokoda Track in 8 days.