The goal of the present paper was to investigate whether soccer referees' nonverbal behavior (NVB) differed based on the difficulty of their decisions and whether perceivers could detect these systematic variations. On the one hand, communicating confidence via NVB is emphasized in referee training. On the other hand, it seems feasible from a theoretical point of view that particularly following relatively difficult decisions referees have problems controlling their NVB. We conducted three experiments to investigate this question. Experiment 1 (N = 40) and Experiment 2 (N = 60) provided evidence that perceivers regard referees' NVB as less confident following ambiguous decisions as compared with following unambiguous decisions. Experiment 3 (N = 58) suggested that perceivers were more likely to debate with the referee when referees nonverbally communicated less confidence. We discuss consequences for referee training.