Schomberg entered the navy in 1788 as captain's servant on the yacht of the Lord Lieutenant of Ireland,, under his father's command. From 1793, at the outbreak of the French Revolutionary War, he served as midshipman aboard and the 74-gun under Captain Thomas Louis. On 30 April 1795 he was promoted to lieutenant, and was transferred to, serving under the Commanders Willoughby Lake and John Cochet, until returning to Minotaur in August 1796. In early 1797 Minotaur was sent to reinforce the fleet off Cádiz and was engaged in several boat actions with the Spanish flotilla and shore batteries. Minotaur remained part of the inshore squadron off Cádiz until 24 May 1798, when she sailed for the Mediterranean, in company with a squadron under the command of Captain Thomas Troubridge. They joined the squadron of Sir Horatio Nelson near Toulon, and subsequently defeated the French at the battle of the Nile in August 1798. During the battle Minotaur fought, and after her surrender she was taken possession of by Schomberg. Between November 1798 and October 1799 Schomberg, now the first lieutenant of Minotaur, was employed on the coast of the Kingdom of Naples. In mid-1800 Minotaur served as the flagship of Lord Keith at the siege of Genoa. On 3 September 1800, under the command of Captain James Hillyar of, Schomberg led the boats of Minotaur in the successful cutting out of the Spanish corvettes Esmeralda and Paz off Barcelona. Schomberg then served as Flag Lieutenant to Lord Keith, aboard, during the Egyptian Campaign. He was sent to Cairo to act as a liaison officer between Keith and the Kapudan Pasha, the commander of Turkish naval forces, during the Siege of Alexandria. Schomberg was appointed acting-commander of the sloop, though it is unclear if he ever took command of her as he was employed onshore until the surrender of the French in September 1801. He was appointed to command of, a 44-gun ship armed en flûte, employed in transporting French troops from Alexandria to Malta, under the terms of the French capitulation. Following the evacuation of Egypt Schomberg was sent on a mission to Tunis, for which Sir Alexander Ball, the Governor of Malta, later presented him with a handsome piece of plate, and for his services in Egypt he was awarded the Imperial Ottoman Order of the Crescent. On 29 April 1802 his promotion to commander was confirmed.
Post-captain
Schomberg was promoted to post-captain on 6 August 1803, and he took command of the 54-gun, stationed as guard ship at Malta. Lord Collingwood nominated Schomberg for command of, but she was wrecked on 27 October 1806. In February 1807 Schomberg took part in the failed Dardanelles Operation under John Duckworth, but on his return to Malta Madras was put out of commission, and he returned to England, after an absence of more than ten years. On his arrival he was appointed to and immediately sailed from Torbay to Lisbon, to announce the imminent arrival of a British squadron, sent to evacuate the royal family of Portugal, as the French were about to enter the country. Unfortunately poor weather and contrary winds meant he arrived off the Tagus after the British squadron, and so negotiations were already underway by Sir W. Sidney Smith, who he then joined aboard Foudroyant as flag captain as they transported the royal family to Brazil in November 1807. Schomberg was later made a Knight of the Portuguese Order of the Tower and Sword. In January 1809 while at Rio de Janeiro Smith appointed Schomberg to command of, but when the Admiralty sent out another captain for that ship, Schomberg was relieved of command, and returned to England in April 1810. In July he was appointed to the frigate, which he fitted out and sailed to the Cape of Good Hope in company with, flagship of Rear-Admiral Robert Stopford. On their arrival Stopford sent Astraea and to reinforce the squadron stationed off the Île de France under Captain Philip Beaver in.
In the absence of Captain Beaver, Schomberg was in command on 20 May 1811, when, the frigates Phoebe and, and the brig-sloop met and defeated a force of three large French frigates that were bringing reinforcements to Mauritius. One French frigate, Renommée, surrendered to Schomberg's ship; Néréide escaped, only to surrender at Tamatave in Madagascar a few days later; and escaped for good. The Battle of Tamatave marked the last French attempt to operate in the Indian Ocean during the Napoleonic Wars. Nearly four decades later the battle was among the actions recognised by a clasp attached to the Naval General Service Medal, awarded upon application to all British participants still living in 1847. In April 1813, following the unexpected death of Captain Beaver, Schomberg took command of, and sailed from the Cape to Brazil, and from there to Portsmouth escorting a large merchant convoy, arriving at Spithead in March 1814. Schomberg was preparing his ship for service in North America, when the Admiralty ordered her to be put out of commission.