In 1760 Baldwin Leighton 6th Baronet (age 12) purchased a Lieutenancy in Captain Jenning's company, which in that same year became part of the 96th Regiment and was posted to India. There Leighton undertook garrison duties at Fort St George before taking to the field. After the Treaty of Paris (1763) the regiment returned to England and was disbanded.

In 1768 Baldwin Leighton 6th Baronet (age 20) purchased a promotion in the 46th Regiment. In 1775, as a captain of grenadiers, he was posted to North America, where he saw action in the New York and New Jersey campaign at Brooklyn, Long Island, the taking of New York, at York Island, White Plains, the storming of Fort Washington and the actions at Rhode Island and Brandywine. He was severely wounded at the action near Monmouth Court House.

On 30 Jan 1817 Baldwin Leighton 6th Baronet (age 70) was appointed Governor of Carrickfergus Castle which position he held until he died in 1828.