Promoted lieutenant on 1 August 1826, Pearson was ADC to the Earl Amherst during his visit to Maharaja Ranjit Singh, who presented him with a sword of honour for successfully riding an hitherto unmanageable horse. He subsequently transferred to the 59th (2nd Nottinghamshire) Regiment of Foot, receiving a captaincy in the regiment on 16 August 1831. On 9 December, he became a captain (by exchange) in the 16th The Queen's Lancers. In December 1843, he fought under Sir Hugh Gough at the Battle of Maharajpur during the Gwalior Campaign and was again decorated. During the First Anglo-Sikh War, Pearson commanded a squadron at the Battle of Aliwal, commanding his regiment during the later part of that battle and again at the Battle of Sobraon, for which he was twice mentioned in dispatches. He received a brevet majority on 19 June 1846, and became a major (by purchase) on 23 April 1847.