The Turkish parliament was the last among the 30 members of the alliance to ratify Finland's membership after Hungary's legislature approved a similar bill earlier this week.
President Tayyip Erdogan said earlier in March that Finland had secured Turkey's blessing after taking concrete steps to keep promises to crack down on groups seen by Ankara as terrorists, and to free up defence exports.
Finland and Sweden asked to join the trans-Atlantic military alliance last year in response to Russia's invasion of Ukraine. But the process has been held up by Turkey and Hungary. The parliaments of all Nato members must ratify newcomers.
Turkey is still holding off approving the Nato membership bid of Sweden, which Ankara says has not gone far enough in cracking down on people Turkey considers terrorists. The three countries signed a pact on the issue last year.
The Turkish parliament's foreign affairs committee unanimously approved the Finland bill last week.
The Turkish legislative process was happening as it prepares for parliamentary and presidential elections on May 14.
Turkey has repeatedly said that Sweden needed to take additional steps against supporters of Kurdish militants and members of the network Ankara holds responsible for a 2016 coup attempt. Turkey treats both groups as terrorist organisations.
Talks between Sweden and Turkey have made little progress, especially following several disputes mainly over street protests by pro-Kurdish groups in Stockholm.
Nato Secretary-General Jens Stoltenberg has said he had urged Turkey and Hungary to ratify both applications.
A vote on Sweden's bid has not yet been scheduled in Hungary.
Reuters