William Ruto attended Kerotet Primary School for his primary school education then joined Wareng Secondary School for his Ordinary Levels education before proceeding to Kapsabet Boys, Nandi for his Advanced Levels. He then went on to receive a BSc (Botany and Zoology) from the University of Nairobi, graduating in 1990.
Ruto was also a member of Christian Union where he served as Chairman. He was ranked the best student in his class. William Ruto later enrolled for MSc in Environmental Science, graduating in 2011. He is currently pursuing a PhD from the same University.
He was Organising Secretary of Youth for Kanu ’92 (YK92), a group that was formed to drum up support for President Daniel arap Moi in the 1992 election. He was first elected to parliament when he won the seat in the 1997 Kenyan election after defeating Reuben Chesire.
Ruto was appointed to the position of Assistant Minister in the Office of the President by President Daniel arap Moi in 1998. He was promoted to be Minister for Home Affairs in August 2002. William Ruto also previously served as the Chairman of the Parliamentary Select Committee on Constitutional Reform in the 9th Parliament. 
One year before elections, Ruto declared publicly that he would stand for the presidency in the next general election, scheduled for December 2007.
Despite being condemned by former president Moi and some of his KANU colleagues, he sought the nomination of the Orange Democratic Movement (ODM) as its presidential candidate. He resigned from his post as KANU secretary general on 6 October 2007.
During ODM Primaries on 1 September 2007, he placed third with 368 votes, behind the winner, Raila Odinga (with 2,656 votes) and Musalia Mudavadi (with 391)
Kenyan presidential election of December 2007 ended in an impasse. The electoral commission declared Kibaki the winner Raila and ODM claimed victory. Kenya was engulfed by a violent political crisis following the dispute over the results. Kibaki and Odinga agreed to form a power-sharing government. Ruto was appointed as Minister for Agriculture In the grand coalition government.
Ruto was transferred from the agriculture ministry and posted to the higher education ministry, swapping posts with Sally Kosgei on 21 April 2010.
On 24 August 2011, William Ruto was relieved of his ministerial duties, and remaining a member of parliament. He joined hands with Uhuru Kenyatta to form the Jubilee alliance for the 2013 presidential election.
He was Secretary General of KANU, the former ruling political party, and MP for Eldoret North Constituency between December 1997 and January 2013.