Mensah represented the Sunyani East constituency in the second, third and fourth parliaments of the Republic of Ghana.
2000 election In the year 2000, Mensah stood in the general election for the third parliament of the Fourth Republic of Ghana and won the seat of member of parliament for
Sunyani East in the
Brong-Ahafo Region. He stood on the ticket of the
New Patriotic Party, the successor to the
Progress Party of the Second Republic. His constituency was among the 14 parliamentary seats out of 21 won by the New Patriotic Party in that election in Brong-Ahafo. The
New Patriotic Party won a majority in parliament with 100 seats in total out of 200 in the third parliament. This was equivalent to 65.1% of the total valid votes cast. He was elected over Captain (rtd) F Adu Kwaku Nkrumah of the
National Democratic Congress, Shiekh Mustapha Abdulah of the
Convention People's Party, Moses Owusu-Yeboah of the
People's National Convention, Boachie Amankwa of the
United Ghana Movement and Boniface Kojo Mensah of the
National Reform Party. These rival candidates won 11,550, 1,269, 1,039, 592 and 427 votes, respectively, out of the total valid votes cast: equivalent to 27.1%, 3.0%, 2.4%, 1.4% and 1.0%, respectively, of the vote.
2004 election Mensah was re-elected as the MP for Sunyani East for the fourth parliament in the 2004 Ghanaian general election. He won 32,035 votes out of 53,972 total valid votes cast or NPP. In all, the NPP won a majority of 128 out of 230 parliamentary seats in the fourth parliament of the Fourth Republic of Ghana. ==Post-1972 coup==