In May 1844 he succeeded Lord Ellenborough as Governor-General of India. He was advanced to Knight Grand Cross of the Order of the Bath on 1 July 1844. Following the death of Maharajah Ranjit Singh tribal war broke out and the first Sikh War ensued in 1845. Hardinge, waiving his right to the supreme command, offered to serve as second in command under Sir Hugh Gough. At the Battle of Mudki on 18 December 1845 Gough commanded the right flank and Hardinge commanded the left flank. After further British successes at the Battle of Sobraon on 10 February 1846, the Battle of Ferozeshah on 21 December 1845 and the Battle of Aliwal on 28 January 1846, Hardinge concluded the campaign with the Treaty of Lahore with Maharajah Duleep Singh on 9 March 1846 and the Treaty of Amritsar with Maharajah Gulab Singh on 16 March 1846. He was created Viscount Hardinge of Lahore and of King's Newton in Derbyshire on 7 April 1846.