Future estimates are indifferent; the Central Intelligence Agency's World Factbook estimated the population of Nauru would decrease to approximately 9,400 in 2014, the United Nations projects the population will stay around 10,000 in the 2020s, and the Nauru Bureau of Statistics estimates the population will increase to 20,000 in 2038.

In Nauru's history, there have been six major demographics changes. The island was first inhabited by Micronesian people roughly 3,000 years ago. The first European to find the island was John Fearn in 1798. In 1888, the country was annexed by Germany. The next demographic change came when Japanese occupied the island during World War II in the 1940s.

 During this time, the Japanese deported several thousands of Nauruans to other islands. The next major demographic change was in the 1960s; the country gained independence, where the percentage of Nauruans started to increase.

 The last major demographics change was in 2006 when the Government of Nauru repatriated almost all of the remaining Tuvaluan and I-Kiribati workers, following large scale reduction from the Republic of Nauru Phosphate Corporation (RONPhos) and government workers.The census of 2006 stated 9,233 people were in Nauru: down 2.13% per year from the previous census of 2002.

From 2002–11, there has been negative net migration, with an annual negative 109 net immigrants from 2006–11. In 2009 there were 1,820 arrivals and 1,736 departures, for a positive rate of 84 immigrants. This was the first time since collecting data in 2002, there was a positive rate.

 Data on arrivals and departures collected by the Nauruan Customs and Immigration Office is not available, so specific immigration data is unavailable. As of the 2011 census, 57% of the population over 15 years old were legally or de facto married, 35% were never married, while 7% were either widowed, separated, or divorced. There are 1,647 households in Nauru, making an average household size of 6.0 persons per household.

Nauru, as of 2011, is mainly inhabited by Naurans (94%), while the main minority groups include Fijian (1%), Chinese (1%), and Solomon Islanders (1%). This shows a major change from the previous major census of 2002, when Nauruans represented 75% of the population. According to the Constitution of Nauru does not exclude any ethnic group to become a citizen.

The Nauruan language is the official language of Nauru. English is widely understood and is used for most government and commercial purposes. According to the 2011 census, 95.3% of the population speaks Nauruan, 66.0% speak English, and 11.9% speak another language. Nauruan is an Austronesian, however, no adequate written grammar of the language has been compiled, and its relationships to other Micronesian languages are not well understood.