Abstract keywords: pragmatic, illocutionary acts, maxim flouting, sitcom, humor this study aimed at finding out the types of illocutionary acts which creates humor effect in the sitcom the big bang theory episode the thespian catalyst (s04e14). a descriptively qualitative study with pragmatic approach was undertaken by observing the utterances spoken by all the characters in the sitcom. the results of the study showed that there were four types of illocutionary acts found in the sitcom; assertive, directive, commissive, and expressive. those illocutionary acts also flouted the maxim of cooperative principles, i.e. quality, quantity, relevance, and manner. in conclusion, it can be known that the humor that occurred in the sitcom is the result of the way the characters conveyed illocutionary acts that also have flouted the maxim as in the cooperative principles.