Ian Adamson was born on 28 June 1944 in Bangor, Co. Down, to John Gamble Sloan Adamson and Jane née Kerr. He was educated at Bangor Grammar School and Queen's University Belfast, where he studied medicine.

Adamson worked as paediatric doctor at the Royal Belfast Hospital for Sick Children from 1974-6, and was subsequently employed as a specialist in community child health and travel medicine by the Belfast Health Trust. In 1998, he was awarded the fellowship of the Royal Institute of Public Health for his services to the health of young people.

Adamson was first elected to Belfast City Council in 1989, representing the Ulster Unionist Party. He served on Council until 2011. He was a Member of the Northern Ireland Assembly from 1998 to 2003.

In 1992, Adamson founded the Ulster-Scots (Ullans) Academy and the Ulster Scots Language Society. He served as a member of the Ulster-Scots Agency from 2003 to 2012. Adamson was appointed as President of the Belfast Civic Trust in 2001. He was awarded an OBE in 1998.