Robert Barlow was born in 1757 in Covent Garden to wealthy mercer William Barlow and his wife Hilaire. The couple had numerous children, including Robert's elder brother George Hilario Barlow who later became Governor-General of India. Robert joined the Navy as a teenager and was promoted lieutenant in 1778, serving on in the American Revolutionary War. In her, Barlow participated in the capture of the French frigate "Minerve" and also was part of the fleet which relieved the Great Siege of Gibraltar.