Abercrombie was born in Buffalo, New York, to Vera June and Donald Abercrombie. Upon graduating from Williamsville High School (now Williamsville South High School), he went on to pursue studies in sociology at Union College in Schenectady, New York. There, Abercrombie obtained his bachelor's degree in 1959. He moved to Honolulu, Hawaii, and studied at the University of Hawai at Mānoa where he obtained his doctorate in 1974. There he attended classes with and befriended current United States President Barack Obama's parents, Ann Dunham and Barack Obama, Sr. As a result, Abercrombie is the only member of Congress to have met Barack Obama when Obama was a child in Hawaii where Obama's parents lived.
Abercrombie first participated in a political campaign in 1970, seeking the Democratic nomination to the United States Senate. Unsuccessful, Abercrombie ran for the Hawaii State House of Representatives where he served from 1975 to 1979. He moved to the Hawaii State Senate, where he served from 1980 to 1986. After Representative Cecil Heftel resigned from the United States Congress in July 1986 to run for Governor of Hawaii, Abercrombie was elected to the House in a September 1986 special election to complete Heftel's unexpired term. However, on the same day Abercrombie lost the Democratic primary for a full two-year term to Mufi Hannemann, who went on to lose to Republican Pat Saiki in the general election.
Abercrombie then set his sights on a seat of the Honolulu City Council. He won the race and served from 1988 to 1990. At the end of his council tenure, Abercrombie once again ran for Congress and won in 1990, and has since been reelected ten times. In the 2008 election, he won with 70.6% of the vote.
Neil Abercrombie is a member of the Congressional Progressive Caucus and has generally compiled a liberal voting record. On October 10, 2002, Neil Abercrombie was among the 133 members of the House who voted against authorizing the invasion of Iraq. On Sunday, March 9, 2009, Abercrombie announced his intention to again run for Governor of Hawaii instead of running for an 11th Congressional term.
Abercrombie is an avid weight-lifter and has a stated goal of lifting 200 lbs more than his age on each birthday. It has been reported and witnessed by other members of Congress that Abercrombie can indeed do this. On his 67th birthday, he bench pressed 268 lbs.