In 1953, Mahathir entered the then Malayan government service as a medical officer upon graduation. He married Dr Siti Hasmah Mohd Ali, on August 5, 1956, and left the government service in 1957 to set up his own practice in Alor Star.
He was active in politics since 1945, beginning with his involvement in the Anti-Malayan Union Campaign; Mahathir joined the United Malay National Organization (UMNO) during its inception in 1946. As State Party Chairman, and Chairman of the Political Committee, he proceeds with his proposal that the selection of candidates be based on certain qualifications for the 1959 general election. Mahathir refused to take part in the national election that year because feel hurt by accusations that he was putting up candidates who were strongly allied to him.
In the third general election of 1964, Mahathir was elected Member of Parliament for Kota Setar Selatan and defeated the Pan-Malaysian Islamic Party's (PAS) candidate with a 60.2% majority. Mahathir won the 1999 general elections mainly due to Chinese votes, when the Malay grounds were split over his misunderstanding with his deputy Anwar Ibrahim.
Mahathir rejoined UMNO on 7 March 1972, and was appointed as Senator in 1973. He was appointed as the Minister of Education. In 1975, he became one of the three vice-presidents of UMNO, after winning the seat by 47 votes. Tun Hussein Onn appointed Mahathir as Deputy Prime Minister on 15 September 1978, and appointed him concurrently as the Minister of Trade and Industry in a cabinet reshuffle.
Lastly, Mahathir became the Prime Minister of Malaysia on 10 July, 1981 when Tun Hussein Onn stepped down due to health problems. He had resigned as Prime Minister on October 31, 2003 after 22 years in office, thus, making him one of Asia's longest-serving political leaders. Upon his retirement on 31 Oct 2003, Mahathir was awarded a "Tun"-ship, Malaysia's highest honor.