His Japan-born children, Joseph and Susanna, were likely expelled to Batavia[9] in 1635 when Tokugawa Iemitsu closed Japan to foreign trade; they disappear from historical records at that time.

He saw naval service against the Spanish Armada in 1588 as master of the Richarde Dyffylde, a resupply ship carrying ammunition and food for the English fleet.

[13] During this service, Jesuit sources claim he took part in an expedition to the Arctic that lasted about two years, in search of a Northeast Passage along the coast of Siberia to the Far East.

[13][b] I am a Kentish-man, borne in a Towne called Gillingham, two English miles from Rochester, one mile from Chattam, where the Kings ships lye: and that from the age of twelve yeares, I was brought up in Lime-house neere London, being Prentise twelve yeares to one Master Nicholas Diggines, and have served in the place of Master and Pilot in her Majesties ships, and about eleven or twelve yeares served the Worshipfull Company of the Barbarie Marchants, untill the Indian Trafficke from Holland began, in which Indian Trafficke I was desirous to make a little experience of the small knowledge which God had given me.

I was hired for chiefe Pilot of a Fleete of five sayle, which was made readie by the chiefe of the Indian Company Peter Vanderhag, and Hance Vanderueke...Adams' fleet consisted of: Jacques Mahu and Simon de Cordes were the leaders of an expedition with the goal to reach Chile, Peru and other kingdoms in New Spain such as Nueva Galicia, the Captaincy General of Guatemala, Nueva Vizcaya the New Kingdom of León and Santa Fe de Nuevo México.

When the ships approached the shores of North Africa, Simon de Cordes realized his rations had been far too generous in the early weeks of the voyage and instituted a 'bread policy'.

At Brava, Cape Verde, half of the crew of the Hoop caught fever and most of the men were sick, among them Admiral Jacques Mahu.

[36] In the same year, Adams secured an authorization letter from Ieyasu to invite the Dutch East India Company to trade with Japan.

[38] In 1607, in response to Adams's achievements, Ieyasu selected him for the high-prestige position of direct retainer in the shōgun's court, entrusting him with territories and swords from Miura-gun (now a part of Yokosuka City).

[39][40] Adams also received generous revenues from his service under Ieyasu[d] and was granted a domain in Hemi (ja:逸見) within the frontier of present-day Yokosuka City, with nearly a hundred slaves and servants.

Also in 1607, Ieyasu gave order to Adams and his companions to assist Mukai Shōgen, a chief commander of Uraga naval forces, to build the shogunate's first Western-style vessel.

Two Dutch envoys, Puyck and van den Broek, were the official bearers of a letter from Prince Maurice of Nassau to the court of Edo.

In the same year, Ieyasu sent Adams to Onjuku, where the Spanish galleon San Francisco was wrecked while carrying the interim governor of the Philippines, Rodrigo de Vivero y Aberrucia.

[42] In 1610, after the Nossa Senhora da Graça incident, Ieyasu replaced Jesuit translator João Rodrigues Tçuzu with William Adams as his counselor of affairs with the Europeans.

[44] Adams and Mukai Shogen oversaw the construction of the new ship for Vizcaíno's expedition, San Sebastian, which sank shortly after being loaded and sailed off in October.

[53][54] Tokugawa Ieyasu, influenced by Adams's anti-Catholic counsels and the increase in samurai and daimyos converting to Catholicism (as in the Okamoto Daihachi incident, for example), banished all Portuguese Jesuits from Japan in 1614.

[59] Although Adams had intended to give up his status and property in Japan to make the voyage on the Clove, he changed his mind after returning to Hirado with Saris.

In May, a company of English merchants tried to sell lead in Hirado but failed to find a buyer until, with the help of Adams, the shogunate purchased their entire stock.

[62] Later in the same year, Adams wanted to organize a trade expedition to Siam to bolster profits and help the company's situation, so he bought and upgraded a 200-ton Japanese junk ship, renamed it Sea Adventure, and hired a crew: around 120 Japanese sailors and merchants, several Chinese traders, an Italian, a Spanish trader and Richard Wickham and Edmund Sayers of the English factory's staff.

On 27 January 1615, the ships under Adams's command, carrying £1,250 in silver, £175 of Indian cottons, and a stock of Japanese weapons and lacquerware, encountered a storm near the Ryukyu Islands.

[64] On 7 December, after a trip to Edo to meet with the ambassador from New Spain on Shogun Ieyasu's orders, Adams left Hirado for Ayutthaya in Siam on the refitted Sea Adventure, intent on obtaining sappan wood for resale in Japan.

[65] In Bangkok, Adams met with the King of Siam and obtained a trading license for the English, then sailed the Sea Adventure to Japan with 143 tonnes of sappan wood and 3,700 deer skins, returning to Hirado within 47 days.

While Hidetada confined English trading activities to Hirado and Nagasaki and barred Japanese merchants from purchasing goods from foreigners in Osaka and Kyoto, Adams retained his hatamoto status and was exempted from these restrictions.

When Adams reached Osaka with his ship Gift of God in September 1617, he met with Hidetada at Fushimi Castle and obtained new Red Seal licenses.

[72] From March until August 1619, Adams undertook a final voyage to Cochinchina and Tonkin, using a personal Red Seal license rather than working for the English.

[77] Cocks wrote: "I cannot but be sorrowful for the loss of such a man as Capt William Adams, he having been in such favour with two Emperors of Japan as never any Christian in these part of the world.

[84] A common account is that his wife was named Oyuki (お雪) and was the adopted daughter of Magome Kageyu, an official who was responsible for a pack-horse exchange on one of the imperial roads that led out of Edo.

[87] In 1635, Hidetada's successor Tokugawa Iemitsu enforced the Sakoku Edict for Japan to be closed against foreign trading; both Joseph and Susanna disappear from historical records at that time.

[78] In 1931, a grave marked as a Miura family tomb was excavated and skeletal remains discovered there were assumed to belong to Adams, but without DNA evidence this could not be confirmed with certainty.

According to Professor Derek Massarella of Chuo University in Tokyo, Adams was largely forgotten in England until the 1872 discovery of his alleged tomb in Japan led to a proliferation of myths and hyperbolic stories.