He was born into a poor family of eight children and went to attend Ithookwe Primary, Mulutu Intermediary and Kitui School.
He later attended Kenyatta University, where he obtained a bachelor's degree in Education, with majors in Religion and Kiswahili.
Afterward, he worked as a lecturer at Machakos Teachers Training College, where he was dean of students and head of social studies.
Nzimbi was elected the fourth archbishop and primate of Kenya and Bishop of the Diocese of All Saints Cathedral on 16 August 2002 and served from 2002 to 2009.
He attended the GAFCON meeting in Jerusalem in 2008 and supported the creation of the Anglican Church in North America in June 2009.