[5][6] At 16, Halimah Nakaayi won the 400 metres at the 2011 Commonwealth Youth Games held in Douglas, Isle of Man.

In 2012, she ran the second 10 km leg of a marathon relay at a festival celebrating 50 years of Ugandan independence.

[9] In August 2019, Nakaayi won the bronze medal in the event at the African Games behind Hirut Meshesha and Rababe Arafi.

She held off Raevyn Rogers, who made a late surge to claim silver in 1:58.18, while Ajeé Wilson finished third in 1:58.84.

[16] At the World Championships in Eugene, Oregon in July, she didn't make it to the final after finishing eighth in her semifinal in a time of 2:01.05.