He studied law, first with Henry Swift of Dutchess County, then with Samuel Young of Ballston Spa.

He was admitted to the bar in 1818 and commenced practice in Skaneateles as the partner of James Porter.

He was Inspector of Auburn Prison in 1838 and 1839, and District Attorney of Onondaga County in 1839.

On June 7, 1847, Jewett was elected one of the first judges of the New York State Court of Appeals.

He was re-elected in 1849 to an eight-year term, but resigned in June 1853 on account of ill health.