Recently nominated minister of finance.He belongs to the Orange Democratic Movement and was elected to represent the Gwassi Constituency in the National Assembly of Kenya since the 2007 Kenyan parliamentary election.
Has was very vocal and instrumental in parliament and In September 2012, Mbadi was appointed the Assistant Minister in the Office of the Prime Minister, a position he held until the 2013 general elections.
Mbadi also serves as the minority leader in the National Assembly of Kenya.
[2] He was in the Public Accounts Committee that looked into the National Youth Service Scandal.
On July 25 2024, he was nominated to be Kenya's Cabinet Secretary for Treasury & Economic Planning by William Ruto.