Collingwood was sent to sea at the age of 12 and served for several years on the home station. In 1774 he served on the North American station and saw service at the Battle of Bunker Hill, there winning his lieutenancy (June 17, 1775). In 1776 he was lieutenant of the sloop Hornet in the West Indies and thereafter began his close association with Nelson.
In 1786 Collingwood returned home and, with the exception of one brief command, remained there until 1792. On the outbreak of the French Revolutionary Wars, he was appointed flag captain and took part in Lord Howe's victory on the "glorious first of June," 1794. He later engaged in the blockade of Toulon and took a conspicuous part in Sir John Jervis' victory off St. Vincent (February 1797). In 1799 Collingwood became rear admiral, and he was at sea in the Triumph and other ships until the peace of Amiens in 1802.
On the renewal of war in 1803, Collingwood was at once employed, chiefly in blockading Brest. He remained there until May 1805 (having in the meantime been promoted to vice admiral in May 1804), when he was given command of a small squadron which was intended to reinforce the Mediterranean fleet under Nelson. He placed himself off Cádiz, and there he was joined by Nelson, so becoming second in command at Trafalgar. In this battle he carried out brilliantly the part assigned to him by the commander in chief. With 15 ships he was to attack the rear of the enemy to prevent their escape. On Nelson's death in the battle, command passed to Collingwood, and he had the difficult task of conserving the fleet and its prizes during the storm that followed. For his services he was created Baron Collingwood and granted a pension of Stg 2,000 a year.
The completeness of victory at Trafalgar prevented Nelson's immediate successors from achieving any comparable triumph, but Collingwood held the Mediterranean command with distinction until his death. He died at sea and was buried near Nelson in St. Paul's Cathedral.