Between 1988 and 1992, he served as Member of Parliament (MP) for Tinderet Constituency and briefly as Minister of Commerce in the Moi government.
Arap Sego launched his political bid for the Tinderet Constituency parliamentary seat during the 1988 general elections.
[4] His Ministerial tenure, however ended prematurely when he was sacked just after nine months in office by Moi and replaced by fellow Nandi MP John Cheruiyot.
Whilst en route to submit his nomination papers for the Tinderet seat on a DP Party ticket, he was attacked and escaped narrowly.
In 2005, he was appointed as Chairman of the National Anti-corruption Campaign Steering Committee (NACCSC) created in May 2004 to spearhead the fight against corruption in Kenya.