James S. Mims was born February 10, 1817 in Bladen County, North Carolina to Samuel Alexander Mims and Nancy Ann (Sessions) Mims. Baptized at the age of thirteen, Mims entered the Baptist church and began his religious studies. He first enrolled in the University of North Carolina at Chapel Hill, but was forced to withdraw because of ill health. After regaining his health, he studied privately under the direction of James C. Furman, D.D. Mims then entered Furman Theological Institution, and after a year's study, he transferred to the Newton Theological Institution of Massachusetts.

Upon graduation from Newton in 1842, Mims was ordained at Society Hill, South Carolina. In the same year, he was elected to the position of junior professor at Furman Theological Institution in Winnsboro, South Carolina. Mims taught systematic theology and moved with the institution to Greenville in 1851, becoming the chair of theology in the newly incorporated university. He remained a member of the faculty until his death at the age of thirty-eight in June 1855.

Mims married Sarah Catherine McIver (1825-1901) in 1844, and they had six children: Samuel Peter, Elizabeth B., Nancy Elizabeth, John, Nannie, and James Sessions.