Adamu entered politics in 1977, and was elected to the Constituent Assembly, which drafted the constitution for Nigeria's short-lived Second Republic. He was a pioneer member of the National Party of Nigeria, the first Secretary-General of the NPN in Plateau State from December 1978, and chairman of the NPN in the Plateau from 1982 to 1983, when military rule began again. In 1994, he was appointed to the National Constitutional Conference by General Sani Abacha's administration. In March 1995, Adamu was appointed a minister of state of the Works and Housing ministry, holding this position until November 1997. When the ban on political activity was lifted in 1997, he joined the United Nigeria Congress Party. In 1998, Adamu became a founding member of People's Democratic Party.
Nasarawa Governor
In April 1999, Abdullahi Adamu ran successfully for position of governor of Nasarawa State on the PDP platform. He was re-elected in April 2003. In December 2003, Adamu welcomed Elizabeth II of the United Kingdom on a visit to Karu, where she was entertained by cultural troupes. Adamu promised to make Nasarawa famous with the State's solid mineral natural resources and tourist attractions such as the Farin Ruwa Waterfalls and the flowing Eggon hills. He backed construction of the Farin Ruwa FallsHydro-Electric plant, visiting South Korea in 2004 and later awarding the engineering contract to the South Korean firm Yooshing Engineering. In September 2005, he launched the School Feeding Programme in the State of Nasarawa, which aims to provide a fortified nutritional supplement to primary school children.
Subsequent career
After the end of his two-term governorship, Adamu became Secretary, Board of Trustees of the Peoples Democratic Party. In November 2009, a group of prominent PDP members stated that they would support his candidacy in the 2011 elections for the Nasarawa West Senate constituency. In Feb 2010, Adamu was arrested by the Economic and Financial Crimes Commission for allegedly embezzling $100 million of government money meant for public projects. Adamu was the PDP candidate for the Nasarawa West Senatorial seat in the April 2011 elections. In an interview in February 2011, he dismissed the EFCC case, saying it was based on "mere allegations", and said it would not affect his candidature. In the event, he was elected with 121,414 votes, while his closest rival, retired General Ahmed Abdullahi Aboki of the Congress for Progressive Change, polled 93,050 votes.