Al-Harthi qualified for the Olympics with a time of 10.16 seconds at the 2015 Military World Games. In 2016, his Olympic qualifying time of 10.05 seconds was 0.11 seconds faster than the required time to enter the men's 100 metres. On 13 August, Al-Harthi did not appear in the preliminary round and competed in the sixth race of the heats. Al-Harthi finished in third in his heat with a time of 10.22 seconds. His placing meant Al-Harthi did not qualify as one of the first two runners in his individual heat, and as he also did not have one of the eight fastest times from the remaining runners, Al-Harthi did not progress to the semi-finals. Out of 84 competitors, Al-Harthi finished in a tie for 26th place overall.