William was born in Plymouth Colony, but was sent back to England and returned on "Abigail" in 1635, on same ship as Deacon Edward Rainsford. He was a blacksmith; sold "spirtuous liquors". In 1677 he was a proprietor of Middleboro township, Plymouth. He was an early settler of Sandwich and held office there.
In 1658 the court awarded William Bassett, the Constable of Sandwich, L5 "in regard of the much trouble" he had had, and the "great losse that hee hath lately sustained."
On 5 June 1667 letters of administration were granted to William Bassett Jr. on the estate of William Bassett Sr. deceased.
On 2 June 1669 "William Bassett of Sandwich ... the eldest son and heir of William Bassett sometimes inhabitant of ... Bridgewater ... now deceased" confirmed to "Joseph Bassett of Bridgewater my youngest brother" land in Bridgewater granted him by his father in his lifetime but not legally confirmed.