On 28 March 2013, Muturi won the speakership after a second round of voting by members of the National Assembly, beating former speaker Kenneth Marende by a 219–129 margin.

President William Ruto Muturi was first elected as a member of the Kenya African National Union (KANU) to represent Siakago Constituency in Parliament following a 1999 byelection which was held after the death of Silas Ita who was the Mp.

He won reelection in 2002 and served as opposition chief whip and chair of the Public Investment Committee during the 10th Parliament.

He vied for re-election in 2007, but was defeated by Lenny Kivuti with a small margin in a heavily contested election.

In 2013, Muturi ran for the Mbeere North parliamentary seat as a member of The National Alliance, but lost to Muriuki Njagagua who was running on APK party.