Cao Jun was a son of Cao Cao, a warlord who rose to power in the late Eastern Han dynasty and laid the foundation for the state of Cao Wei in the Three Kingdoms period of China. His mother was Lady Zhou (周姬), a concubine of Cao Cao. As his uncle Cao Bin (曹彬) had no heir, Cao Jun was adopted as Cao Bin's son. In 217, he was enfeoffed as the Marquis of Fan (樊侯). He died in 219 and was succeeded by his son, Cao Kang (曹抗).