As a candidate for UMNO, Najib was first elected to the Dewan Rakyat in 1976, representing the parliamentary constituency of Pekan in an uncontested election after the death of his father. At the age of 23, Najib was also the youngest member of parliament to be elected.
Within the ranks of UMNO, Najib was first appointed as the head of UMNO Youth's Pekan branch and as a member of UMNO Youth's Executive Council (Exco) in 1976. Beginning 1981, he was selected as a member of UMNO's Supreme Council, before winning the post of vice president of UMNO Youth in 1982, succeeding Mokhtar Hashim following his decision to vacant the post.
In 1987, Najib was announced as the Acting Leader of Movement of UMNO Youth by Anwar Ibrahim after Anwar was asked to contest for the post of Vice President of UMNO. Following the complete reorganisation and founding of the "New" UMNO by Mahathir Mohamad in the aftermath of the 1988 Malaysian constitutional crisis, Najib was appointed president of UMNO Youth in 1988.
By 1993, Najib was elected as one of six vice presidents of UMNO in response to Anwar's decision to contest as the deputy president of UMNO. Najib continued to defend his post in party elections held in 1993, 1996 and 2000.
On March 26 2009, Najib won the Umno presidency unopposed. Umno permanent chairman Tan Sri Onn Ismail made the declaration at the outset of the Umno General Assembly at the Dewan Merdeka, Putra World Trade Centre (PWTC)