Nauru had 9,265 residents at end of 2006. The population was previously larger, but in 2006 some 1500 people left the island during a repatriation of immigrant workers from Kiribati and Tuvalu. The repatriation was motivated by wide-scale reductions-in-force in the phosphate mining industry. The official language of Nauru is Nauruan, a distinct Pacific island language, which is spoken by 96% of ethnic Nauruans at home. English is widely spoken and it is the language of government and commerce (Few outside of Nauru speak Nauruan - thus an international language like English is a necessity.)

The top ethnic groups of Nauru are Nauruan (58%), other Pacific Islander (26%), European (8%), and Chinese (8%). All Europeans are of British origin, and most of these have left since independence. The main religion practiced on the island is Christianity (two-thirds Protestant, one-third Roman Catholic). There is also a sizable Bahá'í population (10%) and a Buddhist population (3%). The Constitution provides for freedom of religion. However, the government restricts this right in some circumstances, and it has restricted the practice of religion by The Church of Jesus Christ of Latter-day Saints and members of the Jehovah's Witnesses, most of whom are foreign workers employed by the government-owned Nauru Phosphate Corporation. Literacy on Nauru is 96%, and education is compulsory for children from six to 15 years old, and two more non-compulsory years are offered (years 11 and 12).[40] There is a campus of the University of the South Pacific on Nauru. Before this school was built, eligible students traveled to Australia, New Zealand, etc., for their college educations. Nauruans are among the most obese people in the world. 90% of adults have a higher BMI than the world average. Nauru has the world's highest level of type 2 diabetes, with more than 40% of the population affected. Other significant dietary-related problems on Nauru include kidney disease and heart disease. Life expectancy on Nauru in 2006 was just 58.0 years for males and 65.0 years for females