The former Yugoslav republic will eventually enter under its new name: North Macedonia.
It comes after Greece's MPs backed a deal ending a 27-year row over its northern neighbour's name.
Greece had blocked Macedonia's membership to NATO as they said the name implied territorial ambitions.
The name was controversial for the Greeks because it used the same name as a neighbouring region in northern Greece.
The dispute that lasted nearly three decades, meant that Greece also stopped Macedonia from joining the European Union.
The membership is due to be signed on Wednesday at a ceremony at NATO's headquarters in Brussels.
The move will make Greece the first country to ratify the accession protocol.
More about: Macedonia