Kimani, guided by Boit James in the race, clocked a time of 15:16.11.
Odair Santos of Brazil won silver, clocking a time of 15:17.55.
Another Kenyan, Bill Wilson, clinched the bronze medal in a time of 15:22.96.
The Paralympic Games began yesterday in the Brazilian city of Rio de Janeiro.
African athletes are hoping to record good performances in the event.
Kenya finished the Olympic Games as the best ranked African team, and with the gold medal, will be hoping to replicate the feat in the Paralympic Games too.