Byron's storm-battered squadron arrived at St Lucia on 6 January 1779. The island had recently been captured by Admiral Samuel Barrington's Leeward Islands squadron and ground troops under General James Grant and successfully defended against d'Estaing, who lurked over the horizon in nearby Martinique.
Byron ended up merging the two squadrons, with Barrington as second-in-command and set about trying to lure d'Estaing's forces into battle. In June 1779 he took his fleet to St Kitts to cover the departure of the trade convoy to England. While he was away, a small force from Martinique captured St Vincent while d'Estaing's fleet landed troops on Grenada. Byron rushed to Grenada in the belief that the island was holding out.
An inconclusive action off Grenada on 6 July 1779 saw three of Byron's ships badly damaged as d'Estaing made little attempt to exploit a slight numerical advantage.
Byron eventually withdrew to St Kitts, fortunate that the French did not take his three crippled ships. A second encounter in Basseterre Roads, St Kitts on 22 July saw the French withdraw, heading back to North America while Byron returned to England due to ill health.
He was briefly Commander-in-Chief of the North American Station from 1 October 1779, promoted to Vice-Admiral of the White in September 1780 and was reputedly offered the command in the Mediterranean, but declined it on the grounds of ill-health. He died at home in London on 10 April 1786.
He was survived by his wife, who died in 1790, three daughters who married well, and two sons. The elder, John, a.k.a. Mad Jack (1756–1791) was the father of the poet George, sixth Baron Byron, The second son, George Anson (1758–1793), a naval officer, distinguished himself in the lead-up to the decisive victory ay the battle of the Saints, off Dominica, on 12 April 1782.