Swinhoe was commissioned ensign in the 56th Regiment of Foot without purchase in 1855, serving in the Crimea and reaching India after the 1857 Mutiny. He exchanged into a lieutenancy in the 15th Foot without purchase in 1858 and returned to the 56th Foot in 1859, transferring to the Bombay Staff Corps later the same year. He was at Kandahar with Lord Roberts in 1880, and collected 341 birds there and on the march back to India. These were described in "The Ibis" (1882: 95-126). He was promoted lieutenant-colonel in 1881 and colonel in 1885.