The Terminally Ill Adults (End of Life) Bill was opposed by 286 members of parliament, while 270 voted for it.
The vote brings an end to a two-year debate in parliament about assisted dying.
On two previous occasions in 2024 and 2025, the elected House of Commons had backed the bill, but it did not become law because it was effectively filibustered by unelected lawmakers in the revising House of Lords chamber.
The bill had proposed allowing adults in England and Wales, with fewer than six months to live, to apply for an assisted death subject to the approval of two doctors and an expert panel.
The government took a neutral stance, saying it was a matter of conscience.
The new UK leader, Prime Minister Andy Burnham, did not vote because he said he did not want to “unduly influence the debate”.
