Isaac Toucey was born in 1796 in Newton, Massachusetts. He studied the law, was admitted to the state bar in 1818, and then established a law practice in Hartford, Connecticut.

From 1821 to 1835, Toucey served as prosecuting attorney for Hartford County before being elected to the United States House of Representatives. He served two terms before being defeated in 1839. Toucey then returned home and resumed his law practice before heading back to his old job as Hartford County's prosecuting attorney in 1842. He served three years before making a failed bid to become Connecticut's Democratic governor in 1845. One year later, he tried again and was successful, but he served only one term before his party refused to nominate him for reelection.

In 1848, President James K. Polk tapped Toucey to become his attorney general following the resignation of Nathan Clifford. Toucey served until the end of the Polk administration in 1849, also serving as acting secretary of state when James Buchanan was away from his post. In 1850, Toucey was elected to the Connecticut state legislature, where he served until 1853; at that point, he was elected to the United States Senate.

Toucey resigned his Senate seat four years to accept President James Buchanan's offer to become secretary of the Navy, a post he held throughout Buchanan administration. Following that stint, Toucey returned to Hartford and resumed his law practice. Isaac Toucey died in 1869.