To follow up on the detail arising out of the convention, the Discovery was recommissioned on 15 December 1790 with Vancouver promoted to Commander as leader of a two-ship diplomatic and exploratory expedition with the 133-ton brig Chatham under Lieutenant William Broughton as her consort.
Vancouver was to proceed to the Sandwich Islands (Hawaii) via the Cape of Good Hope, and Australia's southern coast, spend the winter surveying there and then continue to America's north-west coast. There, he was directed to explore from 30° to 60° N, investigate the Strait of Juan de Fuca, thought to be the entrance to an extensive inland sea, and visit Nootka Sound to receive back the properties the Spanish had seized in 1789.
Well equipped with 'the latest chronometers and scientific instruments', the two ships left Falmouth on 1 April 1791. En route to Hawaii, Vancouver examined the south-west coast of Australia, making the first known European visit to King George Sound (site of modern-day Albany) and Dusky Sound in New Zealand. Plans to determine whether New Holland and Van Diemen's Land were joined were foiled by adverse winds, though Vancouver did manage to survey some 480 kilometres of the coast as far as the westernmost portion of the Recherche Archipelago.
After three weeks taking on wood and water and making minor additions to Cook's survey at Dusky Bay, Vancouver moved on to Tahiti. The two ships became separated en route, with Broughton adding the Chatham Island, east of New Zealand to the chart. After refitting the two vessels in Tahiti, Vancouver spent thirteen days in the Hawaiian Islands where he had expected to find the store ship Daedalus. She sent from Sydney's Port Jackson by Arthur Phillip to replenish Vancouver's supplies and equipment, but she had moved on after her commander and an astronomer, William Gooch, were murdered in Hawaii and some of the crew deserted. She eventually made the rendezvous with Vancouver at Nootka in August 1792.