He once served as the Minority Chief Whip in parliament prior to the Ghanaian parliamentary election in 2008.
On 21 November 2015, Mensah lost the NDC parliamentary primaries to Sam George, bringing an end to his 20 years tenure in parliament.
[7] At the beginning of The Fourth Republic, he was appointed Minister for Youth and Sports by President Jerry Rawlings.
In January 2010, after a cabinet reshuffle, President John Atta Mills appointed him Minister for Employment and Social Welfare.
[10] On 12 February 2021, Mensah was unanimously elected as the representative of Council of State for the Greater Accra Region.