Wanjiru set a 20 Kilometres race walk African Record when she won the event at the 2010 African Championships clocking 1:34:19 hours. The previous record (1:36:18) was held by Susan Vermeulen of South Africa and set in 1999. Wanjiru was already the reigning Kenyan record (time 1:39.50) holder, setting it when she won the 2008 African Championships title. Previously in 2004, she had set a new 20 kilometres national record (1:41:00) in Nairobi.