In 1948, with the formation of PEPSU Mahendragarh territory from Patiala State, Dadri territory (Now Charkhi Dadri) from Jind State and Bawal territory from Nabha State were constituted into Mahendragarh district with the headquarters at Narnaul. At that time, there were three tahsils, namely; Narnaul, Charkhi Dadri and Bawal and Mahendragarh was a sub-tahsil. In 1949, Mahendragarh sub-tahsil was made a tahsil. In 1950, Bawal tahsil was broken up and 78 villages were transferred to Gurgaon district forming Bawal as a sub-tahsil and remaining villages were added to Narnaul and Mahendragarh. Since the merger of PEPSU with Punjab in 1956, the Mahendragarh district became one of the 19 districts of the then Punjab.

The limits of Gurgaon and Mahendragarh districts varied on December 22, 1972. The Rewari tahsil (except 61 villages ) was excluded from Gurgaon district and included in Mahendragarh district . The number of villages, as shown below, was included in Mahendragarh district from Gurgaon district:-
Tahsil/sub-tahsil Number of villages Total
Inhabited Uninhabited
1. Rewari 249 12 261
2. Bawal sub- tahsil 74 1 75
3. Pataudi (sub-tahsil partly) 25 4 29
348 17 365
The Charkhi-Dadri sub- division was excluded from Mahendragarh district and included in the newly constituted district of Bhiwani. In 1977, 81 villages of Rewari tahsil was constituted into Bawal tahsil. In 1978. the district comprised 4 tahsils (Mahendragarh , Rewari, Narnaul and Bawal);