The principal, best known as simply Principal, is a minor character in the books. Like Mrs., his first and last name are unknown. He is described by Junie B. as a "baldy man". He is the main headmaster at the school. In the kindergarten books Junie B. got sent to his office a lot, but in first grade books she isn't. In Junie B. Jones & the Stupid Smelly Bus, he sternly scolds Junie B. for hiding in the closet and not getting on the bus. Principal also seems to has a sense of humor, He points this out in the last kindergarten book after she was sent over for an inappropriate poem about smelly feet.

Principal is described to be a nice person but he's strict and impatient. He has a woman in his office described by Junie B. as "the grouchy typing lady". He is seen less often in her first grader novels although he is still the current principal.