The aim of this study was to investigate performer nonverbal behaviour in popular music performance in order to understand the use and functions of gestures, postures, and facial expression. To this end, the study begins by reviewing relevant psychological and sociological research including Ekman and Friesen and Argyle's categorisations of nonverbal behaviour. Drawing on these specific categories, functions of nonverbal behaviours in popular music performance are proposed. These include: to maintain performer self-control; to provide musical, narrative, emotional and personal information; to regulate and manipulate relationships between performer, co-performer and audience. The investigative work focuses on a case study of The Corrs and is carried out by observing two commercially available film recordings of the band in live performance. The songs demonstrate that within this band, three of the four members take turns singing solos. In the first performance, What can I do? is sung by Andrea (principle vocal), and in the second performance, No frontiers is sung by Sharon and Caroline. Focusing on the soloists, all their nonverbal behaviours are classified in terms of types ( e.g., emblem, illustrator, regulator, adaptor, affect display) and frequency of behaviour. The results demonstrate that Ekman and Friesen and Argyle's categorisations provide a complete description of the nonverbal behaviours found in the performances. Moreover, the analysis reveals differences between individuals and the two songs. With these findings, the paper concludes that nonverbal behaviours in this type of performance are crucial to the development, production and perception of the musical performance. Though preliminary, the study indicates a need for much more detailed research of this topic if performers, educators and researchers are to understand and exploit the nonverbal aspects of a musical communication fully.