Citizenship in Tanzania is governed by the 1995 Citizenship Act. The law is one of the few laws in Africa which provides, on the face of it, for attribution of citizenship on the basis of birth in the territory. However, the law is not applied this way in practice; children of foreign parents born in Tanzania, in particular refugees, are not recognized as citizens (see annex in Going Home or Staying Home). The law prohibits dual citizenship for adults, but not for children.

Tanzania has historically had very low rates of birth registration, creating greater risks of statelessness. In 2006, the UN Committee on the Rights of the Child recommended that Tanzania make greater efforts to expand access to birth registration, particularly in rural areas. The registration of children under five doubled between 1999 and 2010 (but still stood at only just over 16 per cent); and only 26 percent by 2015. The same year, the CRC committee repeated its call for greater efforts on birth registration. More recently, there have been efforts to boost this number by rolling out registration of births by mobile phone. By 2022, birth registration of under-fives had increased to 68 percent.

Tanzania has provided greater access to citizenship for refugees than most African countries. Most recently, in 2008, Burundian refugees who had been living in the country since 1972 were offered the opportunity to naturalise in a procedure. Five years later, the majority of this population still had not been able to access citizenship documents; however, by 2014 the process was revived and most obtained confirmation of their Tanzanian citizenship. In 2023, the government also granted citizenship to more than 3,000 people of Mozambican descent, mostly living in Zanzibar who were very long-term residents and/or born in the country.