1. Kidding and joking can both mean to playfully tease someone else. 2. Joking can additionally mean that someone is simply telling jokes. 3. Kidding can also be used in such a way that the subject and object are the same. (To kid oneself) 1 - I'm just kidding. (Okay) 1 - I'm just joking. (Okay). 2 - He joked about his new job. (Okay) 2 - He kidded about his new job. (Not okay) 3 - He's kidding himself if he really thinks he will win. (Okay) 3 - He's joking himself if he really thinks he will win. (Not okay)