Wangui began her 2008 season with a win at the Chiba International Cross Country. At the 2008 African Championships in Athletics she finished fourth in 10,000 m behind a trio of Ethiopian's led by Tirunesh Dibaba. At the national Olympic trials she won the 10,000 m and came second over 5000 m. Despite her wish to compete in both events, the Kenyan selectors instead chose her just for the 10,000 m, choosing Vivian Cheruiyot for the shorter distance instead. In her second outing on the Olympic stage at the 2008 Beijing Games she finished seventh in the 10,000 metres, running a personal best time of 30:39.96 minutes.