Calvin's mother is a stay-at-home parent who is frequently exasperated by Calvin's antics. Prior to Calvin's birth, she worked a stressful job filled with aggravation, which Calvin's father claims is the reason she was better prepared to stay at home and raise Calvin. Whether he was jesting or not is debatable. On the rare occasions when she is not reacting to Calvin's misbehavior, she seems to enjoy quiet activities, such as gardening and reading The "Daily Disciplinarian."

She is frequently the one forced to curb Calvin's destructive tendencies; once she allows Calvin to smoke a cigarette in order to teach him how unpleasant smoking can be. She also usually seems sympathetic towards her son's relationship with Hobbes, and a few times has found herself speaking to Hobbes as well (although she refers to one instance as "talking to a stuffed animal").

Although Calvin's behavior drives his mother crazy (Calvin once quipped "another day, another gray hair for Mom!"), she still loves him very much. When Calvin was lost on a trip to the zoo, she became sick with worry, and was thrilled when his dad brought him back.
She has also stepped in when his father goes too far with his own private jokes, going so far as to say "I know somebody who's going to get a lot of coal in his stocking, buster." She frequently scolds her husband for his sarcasm in dealing with their son.
Finally, she is sometimes able to calm Calvin down when he is in a bad mood, offering peanut-butter crackers, comic books and other treats to cheer him up