Was the son of Chatar Singh Atarivala. He was appointed governor of Peshawar in October 1845, and recalled in August 1846 to Lahore where he was nominated a member of the Council of Regency. He was created Raja in November 1847. In April 1848, Raja Sher Singh commanded the Lahore Darbar troops sent out to Multan by the British Resident to quell the rebellion by Diwan Mal Raj. But on hearing of the humiliation his father, Chatar Singh, who was governor of Hazara, had suffered at the hands of Captain James Abbott, the Assistant Resident, and sore at the British refusal to permit the marriage of his sister who had been betrothed to Maharaja Duleep Singh, Sher Singh left the British camp and went over to Mul Raj along with the Darbar troops.

He moved northwards to join his father, Chatar Singh, at Hazara. Sher Singh's action set into motion a chain of events which set the whole of the Punjab ablaze. From across the Ravi and from the Sind Sagar Doab multitudes of disbanded Khalsa soldiers swelled his ranks. Overnight, he became a leader of Sikh resistance. He proclaimed himself a Servant of the Khalsa and that of the sovereign, and called upon the people to rise in arms and expel the British from their country.

Simultaneously, the rising in the north under his father, Chatar Singh Atarivala, gained popular support. The Sikh contingents at Bannu, Kohat, Tofik, Peshawar and Attock revolted and joined him. On the other hand, without a formal declaration of war, the British commander-in-chief, Lord Sir Hugh Gough, crossed the Ravi on 16 November 1848, with 24,000 men and 65 guns.

Sher Singh fought the British at Ramnagar on 22 November 1848, defeating Brigadier General Campbell's 3rd Infantry Division. The force under his command fought another action on 3 December at Sadullapur engaging the British division commanded by General Thackwell, and crossed over to the left bank of the river. Soon afterwards he joined his father, Chatar Singh, and together they worsted the British at Cheliafivala on 13 January 1849 but in the last action at Gujrat on 21 Febuary 1849 they suffered a heavy defeat. Both Chattar Singh and Sher Singh fled towards Jehlum, pursued by General Gilbert. On 14 March, Sher Singh surrendered to the British commander at Rawalpindi. The Punjab was annexed to the British dominions and Sher Singh along with his father was detained at Atari and then imprisoned at Allahabad. They were later transferred to Fort William at Calcutta from where they were released in January 1854.