Before 1991 Thiruvarur district and Nagapattinam district were part of the Thanjavur district. After that, the present Taluks of Thiruvarur district and Nagapattinam district were separated from the Thanjavur District, and formed the Nagapattinam district.
In the 2011 census of India, Thiruvarur district had a population of 1,264,277. There was a sex-ratio of 1,017 females for every 1,000 males, much above the national average of 929. Scheduled Castes were 34.08% of the population. Scheduled Tribes were .24% of the population. The average literacy of the district was 74.86%, close to the national average.