Unlike prior research examining how emoji communicate emotions and modify intended meanings, the present research examined whether emoji can perform specific speech acts (remind, etc.), and how well users are able to accurately assess their ability to do so. In four experiments senders were asked to assume that they would send a specific emoji to perform a certain speech act, or to choose which emoji they would use to perform that speech act. Senders and receivers indicated their judgments of communicative success (i.e., that the receiver would recognize the speech act being performed). In two studies, receivers also made judgments regarding the intended meaning of the emoji. Participants judged receivers to be likely to recognize the intended meaning conveyed with an emoji, and there was some evidence of communicative success. However, participants significantly overestimated communicative success, and in all studies, receivers were more optimistic about communicative success than were senders.