Finland will become the 31st member of Nato after Turkey's parliament voted to approve its application.
Turkey had delayed Finland's bid to join the West's defensive alliance for months - complaining the Nordic nation was supporting "terrorists".
Sweden, which applied to join Nato at the same time last year, is still being blocked by Ankara over similar complaints.
Any Nato expansion needs the support of all its members.
Finland will now be formally admitted into Nato at its next summit, taking place in July in Lithuania.
Turkish President Recep Tayyip Erdogan gave his approval to Finland's bid earlier in March, praising the country's "authentic and concrete steps" on Turkish security.
But his ongoing hostility to Sweden was clear - as he again accused the country of embracing Kurdish militants and allowing them to demonstrate on the streets of Stockholm.
The two Nordic nations abandoned their traditional military neutrality in response to Russia's full-scale invasion of Ukraine.
Almost overnight, support for Nato membership leapt from an underwhelming one-third of Finns to almost 80%.
