In 1768, as the colonies grew increasingly restless, Adams moved his growing family to downtown Boston. Abigail and John eventually had four children: Nabby, John Quincy, Charles and Thomas Boylston (a fifth child, Susanna, died at the age of one).

The Townshend Acts continued to draw fire in the colonies. Adams' cousin, Samuel Adams, and James Otis circulated letters calling the acts unconstitutional. The royally appointed Governor Bernard ordered the General Court to either rescind the letters or to be dissolved–and by a vote of ninety-two to seventeen, the Court demurred. Governor Bernard dissolved the Court and requested help from the British government. England responded by sending the naval frigate H.M.S. Romney to Boston Harbor. Emboldened by the military help, customs officials began asserting their duties around the city–only to flee to Castle William when the colonists hit back. Adams was appointed to a committee to draft a letter that would be sent to Bernard by Otis, Adams, John Hancock and Thomas Cushing. The letter, like many of the documents that would come out of the colonies during the war, was written in Adams' words. Adams patiently laid out the colonists' complaints and their concerns over Parliament's new approach to the colonies and the infringement of rights.

Adams went on the court circuit during the fall and arrived back to find Boston overrun by British redcoat troops. Major Small drilled his company daily in front of Adams' residence on Brattle Square, and the Sons of Liberty roamed the streets at night. Civil unrest surged just below the surface. Adams began to consider his own role in the upcoming protests and found himself deeply concerned by the obvious intent of the British to tax and subjugate the colonists. He decided that he was an American first and foremost.

Therefore, when his friend Jonathan Sewall approached him and said that Governor Bernard was prepared to appoint Adams, a man of "talent, integrity, reputation and consequence," to be Attorney General for the colony, Adams politely declined. Surprised, Sewall questioned Adams for a reason, and Adams replied that England was creating a "system wholly inconsistent with all my ideas of right, justice and policy." Despite the prestige and pay such an office would offer, Adams could not blindly turn his back on his ideals. Sewall returned in three weeks and again pushed Adams, but the Adams remained steadfast.

Although Bernard later reconvened the General Court in May 1769, the legislators looked warily across the square in front of their building at the British cannon and troops aimed directly at the front door of the legislature. Again, Adams found himself called upon to draft instructions to his cousin, Otis, Cushing, and Hancock. Each recommendation increased Adams' visibility and his position in the fledgling patriotic cause. The 350 Boston Sons of Liberty invited Adams to their August meeting. Likewise, his reputation as an attorney and barrister increased with his successful handling of several major cases, including Rex v. Corbet, where he defended four sailors accused of murdering a British sailor.

On March 5, 1770, church bells began ringing across the city of Boston. Alarmed, Adams and others rushed into the streets to find that troops had fired on a mob near the Town House, killing five–the first casualties of the American Revolution. The following morning, Adams found himself approached by an Irish merchant on behalf of Captain Preston–the head of the British detachment that had fired on the mob. Adams, believing that everyone had the right to counsel and that the law should be impartial, reluctantly agreed to represent Preston in his trial for murder. Adams later said that representing Preston had been "one of the most gallant, generous, manly and disinterested Actions of my whole Life, and one of the best Pieces of Service I ever rendered my Country." Preston was acquitted in a highly controversial trial–although two soldiers were found guilty of manslaughter. Although the decision to represent Preston caused some to second-guess Adams, he remained a popular member of the community and was elected to the General Court in June 1770.

The toll of the unrest in Boston was wearing on Adams and he moved his family back to the country for some peace; he did keep in office in Boston. In April 1771, while drinking tea with Abigail in Braintree, he declared that he would split his time between his family and the law: "Farewell politics!" he said. His promise would not last long. For despite the repeal of the Townshend Acts and the tax on tea, the colonies remained restless. By 1772, he had moved the family back to Boston and reengaged in the patriot cause. Thomas Hutchinson, now governor, declared in 1773 that Parliament was the "sovereign" government of the colonies. The General Court exploded in anger and Adams again found himself drafting a letter on their behalf to the governor. Adams also got involved in a debate over whether judges should be granted crown salaries like the governor. With the governor able to veto any law from the General Court, and the governor now paid and supported by the crown, there was no check or balance on his power. Boston again found itself nearing rebellion. Sam Adams started a Committee on Correspondence that would communicate Massachusetts' problems to other colonies and vice versa. John Adams, for his part, grew more concerned over the possibility of mob rule.

Hoping to keep the growing unrest harnessed in legal matters, Adams proposed the impeachment of the court's chief justice. However, the matter died in the legislature. As mobs marched around the courthouse, though, jurors and some judge renounced their offices. In December of 1773, during the Boston Tea Party, the Sons of Liberty dumped hundreds or cases of tea into the Harbor. "The die is cast. The people have passed the river and cut away the bridge," Adams wrote. Revolution looked the most likely of the increasingly few options to resolve the conflict.