Thomas Pinckney entered Continental service in 1775 after studying law and military subjects in Europe. Commissioned in the First South Carolina Regiment, he undertook recruiting, fortification, and garrison duties before participating in the southern campaigns. He acted as a liaison between French and American forces at Savannah in 1779. As Horatio Gates's aide at Camden in 1780, he was badly wounded and captured, ending his active Revolutionary War service.

After the war he combined plantation management with politics. Elected governor of South Carolina in 1787, he served until 1789 and presided over the state's convention ratifying the federal Constitution in 1788. His wealth rested on slaveholding plantations. Appointed United States minister to Britain in 1792, he confronted unresolved issues concerning frontier forts, commerce, and the aftermath of the peace settlement.

Washington subsequently sent him to negotiate with Spain. The Treaty of San Lorenzo, signed in October 1795, established the boundary between the United States and Spanish West Florida, secured American navigation of the Mississippi, and allowed American merchants to deposit goods at New Orleans for onward shipment. These provisions improved western access to markets. Pinckney's success involved negotiation with Manuel de Godoy amid Spain's changing relations with Britain and France.

Returning home in 1796, Pinckney became the Federalist choice for vice president but finished behind Thomas Jefferson under the original electoral system. He served in the House of Representatives from 1797 to 1801, generally supporting John Adams while opposing the Sedition Act. During the War of 1812 he returned as a major general commanding the Southern Division, supervising defenses and military administration. He later resumed plantation agriculture and became president general of the Society of the Cincinnati in 1825. He died in Charleston in 1828.