This investigation examined precompetitive sleep behaviour of 103 athletes and how it relates to precompetitive mood and subsequent performance. Results revealed that on the night before competition athletes slept well under the recommended target of eight hours of sleep for healthy adults, with almost 70% of athletes experiencing poorer sleep than usual. It was found that anxiety, noise, the need to use the bathroom and early event times were amongst the most commonly reported causes of disrupted sleep in athletes on the night prior to competition. The negative moods of fatigue and tension were both significantly negatively correlated with precompetitive relative sleep quality (r=-0.28, P=0.004, r=-0.21, P=0.030, respectively) and total sleep time (r=-0.23, P=0.023, r=-0.20, P=0.044, respectively). Additionally, tension was positively correlated with number of awakenings (r=-0.20, P=0.045). Vigour was seen to be significantly positively associated with relative sleep quality (r=0.24, P=0.013). The relationships between relative sleep quality and fatigue, tension and vigour accounted for approximately 4"5% of the variance in mood scores. Disrupted sleep did not demonstrate any significant relationship with relative sporting performance. Conclusions from the present investigation are that athletes may be at particular risk of disrupted sleep on the night prior to competition, and this disruption can negatively relate to an athlete’s precompetitive mood states.