The costuming of actors plays a significant role in how their characters and their actions are understood by audiences. This article examines how male transgression is encoded in fictional royal television via costuming. Costumes for royal characters sit at the intersection between dramatic convention and popular expectations of royal behaviour. Little work has been done to date to examine how costume works in this space, even less on fictional male royal costuming. This article demonstrates, via a discussion of the four kings of the television drama The Royals (2015–18), how costuming both engages in narrative expectations and reveals transgressions.