He was educated initially at Kainaur and subsequently at the Khalsa College in Amritsar, and began working in his father's firm in the steel industry.

Baldev Singh won an election to the Punjab provincial assembly under the Government of India Act 1935 in 1937, as a candidate of the Panthic Party.

Singh negotiated an agreement with Sir Sikandar Hyat Khan, the leader of the Unionist Party to form a government in Punjab, and became the provincial Development Minister for a brief time in the summer of 1942.

Baldev Singh was chosen again to represent the Sikh viewpoint to the Cabinet Mission Plan that had arrived to discuss proposals for Indian political independence.

Singh reiterated the Sikh view that India should remain a united country with special protections for the rights of religious minorities.

Singh also insisted that should partition become inevitable, the division of the Punjab should happen in a way to offer territorial protection to the Sikhs from Muslim domination.

Along with Vallabhbhai Patel, the Home Minister, Singh became responsible for leading the Indian Army's efforts to provide security, relief and refuge to over 10 million Hindus and Sikhs who were leaving the newly created Pakistan.

Patel and Singh led from the front, and despite a heavy toll, the Army finally re-asserted peace and rule of law all over India and the borders of Punjab and Bengal.

Defence Minister Singh also led the preparations and planning for the war in Jammu and Kashmir, which had broken out with Pakistani tribesmen and some military officers had made an incursion into the state with the aim of annexing it into Pakistan.

On 28 November 1948, General Roy Bucher had advised Prime Minister Jawaharlal Nehru to agree to a ceasefire because "overall military decision was no longer possible".