Monokuma is often described as easygoing and cheerful at first glance, but with a very sinister undertone. However, he always rather quickly reveals his evil nature by describing killing games and his desire for despair, and he is very well known for his habit to say and do whatever he wants to. He loves hysteria, violence, and chaos, summarized in one of his catchphrases "thrills, chills, kills!". He also has his own signature laughs, a sadistic "puhuhu" ("upupupu" in the Japanese version) and a mocking "ah-hahahaha".

In many ways, Monokuma represents duality both in design and personality, with his white good side and black evil side. He can sometimes act polite or cute and innocent, even patronizing, and during rare moments he even seems to give genuine positive and wise advice. However, he is mostly known for his malicious and cruel side, possessing a twisted sense of humor and a tendency to torment others and do anything for the sake of despair. He can switch between these traits at the drop of a hat, making him unpredictable for his students to deal with. He usually gets excited about the Class trials and does everything he can in order to make them entertaining for himself.