After the war, Pinckney focused on his plantations and his legal practice. In 1787, he ran for the position of Governor of South Carolina at the urging of his friend, Edward Rutledge. Pinckney was elected governor with little opposition. He strongly favored ratification of the United States Constitution and presided over the state convention that ratified the Constitution. He served in the South Carolina House of Representatives for St. Philip's and St. Michael's Parish from January 3, 1791 to December 20, 1791.