According to the census of National Statistics Agency (2011), the prefecture of Kilkis has a population of 80.419 inhabitants. It should be noted that the significant population growth of the county over the last decade is mainly due to the city of Kilkis.

Kilkis has significant population gravity and it also presents an impressive rate of population growth. Specifically, according to the 2001 census, the city of Kilkis gathers 19.6% of the total population of the prefecture, showing a population increase of 43.6% compared to the 1991 census.

The prefecture has a total of 166 towns & villages of which 121 (73%) have a size of less than 500 residents.

The area of Kilkis, after the   population exchange   with   Bulgaria   (1919) and   Turkey   (1923) accepted the installation of many refugees coming from   regions like East Thrace,  Anatolia,   Cappadocia   and Pontos.

It is only natural that its population constitutes of a medley of Greeks and it is considered a multicultural region due to the different origins of its inhabitants. In our days, the prefecture of Kilkis is inhabited by Pontians, Thracians, Vlachs, Sarakatsans, Anatolites, Stenimachites, Stromnitsiotes and local Macedonians, who maintain many of the customs and traditions associated with their origin, and make up the multicultural profile of Kilkis.