Benjamin Kigen comes from Baringo County in western Kenya. He initially started over distances of 1,500–5,000 meters, before specializing in the 3,000-meter obstacle course in 2016. In 2017 he took part in the eliminations for the World Championships in London, but finished fourth in the decisive run and thus missed the qualification. For one month he improved to a time of 8: 11.38 min in a competition in Monaco. In 2018 it improved to a time of 8: 06.19 min.
In July 2019, at the Diamond League meeting in Monaco, he set his current best time of 8: 05.12 minutes and finally made it to the top of the world with further good placements. In August he became Kenyan champion and just one week later he celebrated his greatest sporting success by winning the Africa Games in Rabat. He also qualified for the World Championships in Doha. He survived the preliminary run with ease and finally took seventh place in the final in 8: 06.95 minutes.