The first elections in free India were held in 1952 and Birendra Singh contested as an independent candidate from his native Ahirwal region, of which the city of Rewari is the urban center.

During these years, he was made a minister in the Pratap Singh Kairon government and held charge, at various times, of several important ministries like PWD, Irrigation, Power, Revenue and Consolidation, etc.

Several other princely states in the hills of East Punjab were similarly merged to create the Chief Commissioners' Province of Himachal.

Therefore, beginning 1962, he spearheaded the campaign for division and achieved success when the state of Haryana was born in November 1966.

He was appointed Chief Minister of Haryana on 24 March 1967, replacing Bhagwat Dayal Sharma[10] with his newly formed VHP assuming power.

Congress won the Vidhan Sabha election in 1968 and Bansi Lal became Chief Minister.

[citation needed] He was elected to the 5th Lok Sabha in 1971 from the Mahendragarh on the Vishal Haryana Party ticket.

In 1980, he was re-elected to the 7th Lok Sabha and he played a prominent role in the formation of the Congress Government in the centre.

He joined Janata Dal and was elected to 9th Loksabha in 1989, and became Cabinet minister in the Chander Shekhar's Govt.

[citation needed] Rao Birender Singh also enrolled in the Territorial Army during the Second World War.