Before joining elective Tanzanian politics, Nchemba worked as an economist at the
Bank of Tanzania. Later, President
Jakaya Kikwete appointed him as Minister of Finance and Economic Planning. His tenure at the finance ministry coincided with the "
Tegeta escrow scandal", which involved the embezzlement of hundreds of million of dollars by high-ranking government officials. Nchemba, who was not implicated, maintained that the full extent of the law should apply to those involved. Following the formation of the
6th Cabinet of Tanzania, on 31 March 2021,
Philip Mpango was promoted to
Vice-President of Tanzania, Nchemba took over the post of Minister of Finance and Planning. On 4 July 2023, he retained his position of Minister of Finance, however, the Ministry of planning was moved under the president's office. He was nominated as
Prime Minister of Tanzania by Suluhu on 13 November 2025 following the
2025 Tanzanian general election. ==Other activities==