The district derives its name from “Chagai” a village on the western border of the Lora Hamun. The legend attributes the origin of the name to the numerous wells (Chahas) which are said to have formerly existed in the vicinity.
Very little is known about the ancient history of Chagai. The earliest monuments are the ruins of terraced embankments. These are found at the foot of the Ras-Koh hills; they are ascribed to the fire-worshippers, who are said to have been the inhabitants of this area more than two thousand years ago. The next traces of ancient history are the square shaped tombs in the western areas of the district, which are attributed by the local traditions to the Kianian dynasty of Iran.
The remains of the ruined forts and karezes found in different parts of the district are assigned to the Arabs. These are also sometimes attributed to the Mughals and in any case indicate the presence of a richer civilisation than is now found among the Baloch and Brahvi inhabitants of the district.
The Baloch are perhaps the oldest inhabitants of the district, who according to themselves migrated from Aleppo. The Brahvis, about whose origin there are different theories, must have moved towards the north from their original home in Kalat District and settled down in pockets with a major concentration in the Nushki area. Both the Brahvi and Baloch appear to have been firmly established in the beginning of the 16th century, as is seen from a narrative of the flight of the Mughal Emperor Hamayun along the valley of the Hilman to Seistan in 1543. From the middle to the end of the 16th century, the district remained under the rule of the Safavid dynasty. Later it appears in history as part of the Mughal Empire and with the downfall of the Mughal power, the northern portion of the Nushki was annexed to the territories of Khan of Kalat, Mir Abdullah Khan (1716 - 1730). In 1733 Sher Khan the Baloch, Chief of Nushki, submitted to Mir Hassan, the second son of Mir Wais and the founder of the Ghilzai dynasty. Mir Hassan ruled the adjacent Pathan area now forming Quetta and Pishin districts, and compelled the Baloch and Brahvi tribes to tender their allegiance to.
A few years later, Nadir Shah sent an expedition against Nushki under Muhammad Ali Beg, who inflicted a severe defeat on the Baloch near Shorawak. In 1740 Nadir Shah conferred Nushki as a fief upon the chief of Kharan. Later it was retaken by Mir Nasir Khan, the great Brahvi ruler (1750-1793) and Nushki became a Niabat of the then Kalat State and remained so for about a century.
The advent of the British in this area commenced with the British agreement of 1878 with the Khan of Kalat. Subsequently as a result of the partial survey and definitions of the western boundary with Iran from Kuhak to Koh-i-Malik Siah and demarcation of the Afghan Baloch boundary in 1896, the western Sanjrani (present Dalbandin sub-division and Nokkundi Tehsil) became part of Kalat State. In November, 1896 the first British Political Agent of Chagai was appointed. Nushki continued to be Niabat to Kalat State. Three years later, however the Niabat of Nushki was leased by the British from the Khan on an annual rent of Rs. 9,000. The management of the Niabat was handed over on the 1st July, 1899 to the British Government. This was done with giving all the rights and privileges, as well as full and exclusive revenue, civil and criminal jurisdiction, including all rights to levy dues and tolls. From July, 1899 to the 13th August, 1947 the district remained under the British Government. After independence in 1947 and after the declaration of Balochistan as a province in 1970, Chagai became a district within Quetta Division
The only features of archaeological interest in the district are the remains of ancient forts, karezes, dams and cupolas. Their history is not known and they are ascribed by the inhabitants indiscriminately to either the Arabs or the Mughals. In Dalbandin Tehsil there are ruins of several cupolas in the neighbourhood of Padag and Zarala.
There are several well known shrines in the district. The most important of these are the shrines of Sayyad Bala Nosh near Chagai and that of Sher Jan Agha near Keshingi. The other shrines are of Pir Sultan, Sheikh Hussain, Sayyad Khawaja Ahmad, etc. The Ziarat Ghaibi, Zinda Pir and Chil Ghazi situated in the Nushki Tehsil are also quite famous.