He was born in Southampton into a sea-faring family. He joined the Royal Navy as a cadet in 1872. His first active service was during the Egyptian War of 1882. He was appointed to the Admiralty in 1888. He had a number of commands in the 1890s, and in 1900 he was part of the command for the land relief of Beijing during the Boxer Rebellion, the First Peking Relief Expedition.
Under John Fisher he was Director of Naval Ordnance (1905-1907) and then Controller of the Navy (1908-1910). Jellicoe pushed hard for funds to modernise the navy, supporting the construction of new designs of dreadnought and submarine.
In 1911 Jellicoe became deputy to George Callaghan, the Commander of the Grand Fleet. At the start of WW I, August 4, he was promoted to command the Grand Fleet. He was in command of the fleet at Jutland (1916), where his caution was later criticized. He was made First Sea Lord in November 1916, succeeding Henry Jackson. But his refusal to institute the convoy system lead to his replacement in 1917 by Rosslyn Wemyss, then David Beatty. He was made a viscount in 1918.