[5] He was initially bowling medium pace, but he later transformed into a spinner after being convinced to do so by Samuel Walusimbi who had represented East Africa at the 1975 Cricket World Cup.
[5][6] Nsubuga made his international debut playing for East and Central Africa in the 1997 ICC Trophy[7] when aged just 16.
Uganda won the tournament, with Nsubuga named man of the match in the final against Argentina after scoring 55 from 38 balls and taking 4/27.
[10] In July 2018, he was part of Uganda's squad in the Eastern sub region group for the 2018–19 ICC World Twenty20 Africa Qualifier tournament.
[18] In July 2019, he was one of twenty-five players named in the Ugandan training squad, ahead of the Cricket World Cup Challenge League fixtures in Hong Kong.
[20] In November 2021, he was named in Uganda's squad for the Regional Final of the 2021 ICC Men's T20 World Cup Africa Qualifier tournament in Rwanda.
[24][25] On his first T20 World Cup match against the Papua New Guinea, he displayed a scintillating bowling performance restricting the opponents to just 77 runs with a tight bowling spell giving away only four runs in his four overs and also captured two wickets in addition to two maiden overs, giving no room for the batsmen to work with.