It was formed on January 1, 2001, by the amalgamation of the village of Markdale and the townships of Artemesia, Euphrasia and Osprey, which included the unincorporated hamlets of Eugenia, Ceylon, Maxwell, Singhampton, Priceville, Kimberley, Badjeros, and Feversham.

The former village of Flesherton is also located within the municipality and was amalgamated with Artemesia Township in 1998.

According to the 2016 census, the municipality covers a land area of 882 square kilometres and has a population of 9,804.

The dominant natural feature of the area is the Niagara Escarpment, which passes through the municipality and has several ancillary features: In the 2021 Census of Population conducted by Statistics Canada, Grey Highlands had a population of 10,424 living in 4,091 of its 5,337 total private dwellings, a change of 6.3% from its 2016 population of 9,804.

[6] Elementary students (kindergarten to grade 8) are divided into three catchment areas: All of those students go to Grey Highlands Secondary School, in Flesherton, for Grades 9 to 12.