Samuel Adams was born in Boston in the British colony of Massachusetts on September 16, 1722, an Old Style date that is sometimes converted to the New Style date of September 27. Adams was one of twelve children born to Samuel Adams, Sr., and Mary (Fifield) Adams in an age of high infant mortality; only three of these children lived past their third birthday. Adams's parents were devout Puritans and members of the Old South Congregational Church. The family lived on Purchase Street in Boston. Adams was proud of his Puritan heritage, and emphasized Puritan values in his political career, especially virtue.
Samuel Adams, Sr. (1689–1748) was a prosperous merchant and church deacon. Deacon Adams became a leading figure in Boston politics through an organization that became known as the Boston Caucus, which promoted candidates who supported popular causes. The Boston Caucus helped shape the agenda of the Boston Town Meeting. A New England town meeting is a form of local government with elected officials, and not just a gathering of citizens; according to historian William Fowler, it was "the most democratic institution in the British empire". Deacon Adams rose through the political ranks, becoming a justice of the peace, a selectman, and a member of the Massachusetts House of Representatives. He worked closely with Elisha Cooke, Jr. (1678–1737), the leader of the "popular party", a faction that resisted any encroachment by royal officials on the colonial rights embodied in the Massachusetts Charter of 1691. In the coming years, members of the "popular party" became known as Whigs or Patriots.
The younger Samuel Adams attended Boston Latin School and then entered Harvard College in 1736. His parents hoped that his schooling would prepare him for the ministry, but Adams gradually shifted his interest to politics. After graduating in 1740, Adams continued his studies, earning a master's degree in 1743. In his thesis, he argued that it was "lawful to resist the Supreme Magistrate, if the Commonwealth cannot otherwise be preserved", which indicated that his political views, like his father's, were oriented towards colonial rights.
Adams's life was greatly affected by his father's involvement in a banking controversy. In 1739, Massachusetts was facing a serious currency shortage, and Deacon Adams and the Boston Caucus created a "land bank" which issued paper money to borrowers who mortgaged their land as security. The land bank was generally supported by the citizenry and the popular party, which dominated the House of Representatives, the lower branch of the General Court. Opposition to the land bank came from the more aristocratic "court party", who were supporters of the royal governor and controlled the Governor's Council, the upper chamber of the General Court. The court party used its influence to have the British Parliament dissolve the land bank in 1741. Directors of the land bank, including Deacon Adams, became personally liable for the currency still in circulation, payable in silver and gold. Lawsuits over the bank persisted for years, even after Deacon Adams's death, and the younger Samuel Adams often had to defend the family estate from seizure by the government. For Adams, these lawsuits "served as a constant personal reminder that Britain's power over the colonies could be exercised in arbitrary and destructive ways".