Every person born in Nigeria before or after the date of independence (1960) either of whose parents or any of whose grandparents belong to an indigenous community or is a citizen of Nigeria, are classified as citizens of Nigeria by birth, as is every person born outside Nigeria either of whose parents is a citizen of Nigeria.
A foreign woman who marries a citizen of Nigeria, and a person who is of adult age (18 years old), born outside Nigeria but with a Nigerian grandparent, are allowed to apply for and hold Nigerian citizenship by registration.
A person who has made or is capable of making a useful contribution to the advancement, progress and well-being of Nigeria; who is of full age and capacity; has been assimilated into the way of Nigerians; and has been largely resident in Nigeria, may be qualified to apply for a certificate of naturalisation.
Dual citizenship is allowed for persons who have a Nigerian parent, that is, citizens by descent, according to Section 25 of the 1999 Nigerian Constitution. Dual citizenship is also allowed for persons who were born in Nigeria after October 1, 1960, and have either a Nigerian parent or grandparent.
As applicable in Section 28 of the Constitution, a citizen who holds Nigerian Citizenship, by means other than birth, but acquires or retains the citizenship of another country by means other than birth, must forfeit their Nigerian citizenship. A person may obtain Nigerian citizenship as a second citizenship if his or her first citizenship was obtained by birth. Acquisition of Nigerian Citizenship by registration or naturalisation is therefore conditional upon renunciation of citizenships of other countries not obtained by birth.