He went to Embomir Primary School and Kerio ValleySecondary school, from which he graduated in 2004. He did not take up running until 2007, later quoting "I saw I was not making any progress in life and my family needed assistance". Kitwara won four national cross-country circuit competitions in 2008, but failed at the trials for the cross-country world championships. In 2008 he took to the European road running circuit and won at the 20 Kilomètres de Paris, Dam tot Damloop and Singelloop Utrecht races. Kitwara, a policeman by occupation, won the 2009 Rotterdam Half Marathon in a time of 58:58 – a course record which made him only the sixth runner to complete a sub-59-minute run. Earlier in the year Kitwara won another major half marathon, the City-Pier-City half marathon in The Hague, beating Haile Gebrselassie into second place, as well as winning at the Peachtree Road Race. He set a new course record of 27:25.6 at the World's Best 10K in February that year. Kitwara won the 10,000 m race at the Kenyan Trials in June 2009, earning a place in the national team for the 2009 World Championships in Berlin. However, he was subsequently removed from the team by Athletics Kenya for participating in road races after the Trials. He did, however compete at the 2009 IAAF World Half Marathon Championships in Birmingham, finishing 10th. He began 2010 with two second-place finishes: finishing just behind Tilahun Regassa at the Abu Dhabi Half Marathon, and recording 59:47 minutes for second at the Lisbon Half Marathon behind a world record-beating Zersenay Tadese. Kitwara is a three-time champion of the Bay to Breakers and the course record holder in that event. In 2009, race organizers reported that his 33:31 was the fastest 12 km ever run. In 2010, he edged out fellow Kenyan Peter Kirui by less than a second for the victory in 34:15. He ran a personal best for the 10K at the Utrecht Singelloopin September 2010, finishing as runner-up with a time of 27:11 minutes. This elevated him into the top eight of all-time, although race winner Leonard Komon overshadowed this achievement by breaking the world record by a large margin. Kitwara took his second win at the World's Best 10K in February 2011, becoming one of three men to have won twice in Puerto Rico. He was out-stripped at the City-Pier-City race in March, however, as he came fifth while Lelisa Desisa won the race. He won his second title at the Peachtree Road Race in July that year. Later that year he ran a 58:48-minute personal best for second place at the Philadelphia Half Marathon, making him the fourth fastest runner ever for the distance. He did not reach the same form in November, when he came fourth at the Delhi Half Marathon. He opened 2012 with another win at the World's Best 10K, completing the course in 28:02 minutes. He attempted a marathon debut at the Rotterdam Marathon, but did not finish as he dropped out after 30 km. In October, he was placed fourth at the 2012 Chicago Marathon with a time of 2:05:54 hours. He won his third straight World's Best 10K title at the beginning of 2013. A return to the Rotterdam Marathon saw him complete the distance, although his time of 2:07:22 hours was slower than his last. At the 2015 London Marathon he came 6th in 2.07.43. Kitwara won the 2016 Lisbon half marathon in 59.47 some way off his personal best.
