The territory of Kardzhali province was acquired by Bulgaria during the First Balkan War in 1912. In 1913 the region was organized as the district (окръг, okrag in Bulgarian) of Mestanli. This district was part of Stara Zagora province from 1934 until 1949, then it was transferred to the newly formed Haskovo district. In 1959 Kardzhali became the center of a new district with similar borders to the current province. Between 1987 and 1999, the region was part of Haskovo Province, after which it was restored, now as a province and with slightly changed borders.
The Kardzhali province (област, oblast) contains seven municipalities (singular: oбщина, obshtina - plural: общини, obshtini). The following table shows the names of each municipality in English and Cyrillic, the main town (in bold) or village, and the population as of 2009.
According to the 2011 census, Muslims are 82,227 (70,14% of the answered) and the Orthodox are 23,916 (20,4% of the answered). The Muslims' figure is made up of Turks and of significant part by Muslim Bulgarians, though the Orthodox are the majority among the Bulgarians in the province.
In the 2001 census, 149,839 people of the population of 164,019 of Karzhali Province identified one of the following as their religion (with percentage of total population):