The application was prompted by the invasion of Ukraine by Russia, with which Finland shares a long border.
Finland will become the 31st member of NATO on Tuesday, the Western military alliance's secretary general has announced.
The application was prompted by the invasion of Ukraine by Russia, with which Finland shares a long border.
North Atlantic Treaty Organization, also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two North American.
Turkey had delayed the application, complaining that Finland was supporting "terrorists".
Sweden applied to join NATO at the same time last May, but Turkey is blocking it over similar complaints.
Turkish President Recep Tayyip Erdogan has accused it of embracing Kurdish militants and allowing them to demonstrate on the streets of Stockholm, BBC reports.
Any NATO expansion needs the support of all its members.
"We will raise the Finnish flag for the first time here at NATO headquarters. It will be a good day for Finland's security, for Nordic security and for NATO as a whole," NATO Secretary General Jens Stoltenberg said in Brussels.
"Sweden will also be safer as a result," he said.
Finland's membership is one of the most important moments in NATO's recent history.
Finland, a country with a 1,340km (832 mile) border with Russia and one of the most powerful arsenals of artillery pieces in Western Europe, decided to ditch its neutrality and join the alliance in response to Russia's full-scale invasion of Ukraine.
Sweden also abandoned a longstanding commitment to neutrality in applying to join NATO, but unlike its neighbour, it does not share a border with Russia.
One of NATO's founding principles is that of collective defence - meaning an attack on one member nation is treated as an attack on them all.