He was the Indian National Congress nominee on the Radcliffe Commission that defined the boundaries of India and Pakistan.

Mehr Chand Mahajan was born on 23 December 1889 at Tika Nagrota in the Kangra district of Punjab, British India (now in Himachal Pradesh).

His father, Lala Brij Lal, was an advocate, who later established a reputed legal practice at Dharmsala.

On 15 October 1947, Mahajan was appointed the Prime Minister of Jammu & Kashmir and played a role in the accession of the state to India.

Before becoming Chief Justice he served as one of the first Judges of the Supreme Court of independent India from 4 October 1948 to 3 January 1954.