Better understanding how audience size influences emotions and behaviours during public performances is of particular importance since it may both impact the level of anxiety and quality of achievement of the performer and alter the degree of appreciation of the observer. We tested this question in a naturalistic setting by analyzing self-assessment questionnaires, Galvanic skin responses and behaviours of actors and spectators during theatrical representations with small, medium and large audiences. We found that: actors and spectators differed in their perception of the effects of audience size; the different components of emotions (cognitive, physiological, behavioural) were affected differently by audience size, which was also modulated by the individual’s status; actors and spectators differed in their representation of the others’ emotional state. Although our study remains exploratory, our findings highlight the complexity of the audience effect when comparing observers’ and performers’ emotions.