He served in the Parliamentary army in 1647 and 1648 and, during his father's protectorate, was a member of the Parliaments of 1654 and 1656. In 1655 he was appointed to the committee of trade, but he showed little of his father's ability, and it was not until 1657, when a new constitution gave Oliver the right to choose his successor, that the Lord Protector began to groom his son for high office. In July 1657 Richard succeeded his father as chancellor of the University of Oxford. He became a member of the council of state on December 31, and about the same time he obtained a regiment and a seat in Oliver's House of Lords. On his deathbed Oliver may have designated Richard as his successor; Oliver died on Sept. 3, 1658, and Richard was immediately proclaimed lord protector.

The new ruler soon encountered serious difficulties. He offended high-ranking army officers by taking personal charge of the army, thereby ignoring their request for the appointment of an experienced officer as commander in chief. In addition, conflict between Parliament and the army caused the army to establish a council to plot its strategy. When Parliament forbade the council to meet without Richard's permission, the council seized power and forced Richard to dissolve Parliament (April 21, 1659). The officers now recalled the Rump Parliament, which had been dissolved by Oliver in 1653. The Rump dismissed Richard, and on May 25 he officially abdicated. Having amassed large debts during his tenure of office, he escaped his creditors in 1660 by going to Paris, where he lived for a time as John Clarke. Eventually he moved to Geneva. In about 1680 he returned to England and lived in seclusion at Cheshunt until he died.