Mutai grew up in Cheptigit, a village near Kaptagat, Uasin Gishu County in the Rift Valley Province, and his extended family includes Richard Limo, the 2001 World Champion over 5000 metres. Mutai began to make an impact domestically at the age of eighteen, taking third place over 10,000 metres at the Rift North Province Championships in 28:09.2 minutes.