Mood state changes are widely regarded as a symptom of athlete burnout and show potential to be used as a marker for this condition. The aim of this study was to determine whether changes in burnout scores would be accompanied by similar changes in mood state scores, and to determine the strength of the relationship between burnout and mood state scores at different test points. Forty-one male student rugby union players (mean age: 22.26 ± 1.39 years) completed the Athlete Burnout Questionnaire (ABQ) of Raedeke and Smith (2001) and the Stellenbosch Mood Scale (STEMS) of Terry, Potgieter and Fogarty (2003) on a three-weekly basis over a five-month pre-season training, pre-competition and competition phase. Data collection consisted of seven test points in total during this period. The ABQ subscale scores remained unchanged throughout the study period, whereas practical significant fluctuations in Total Mood State, Depressive Mood, Anger, Fatigue and Confusion were evident. Practical significant correlations (relationships) were observed between various Burnout and Mood State subscales, notably at test points T1 (start of the pre-season training phase), T4 and T5 (pre-competition phase). The Emotional/Physical Exhaustion and Total Burnout Score in particular were strongly related to various STEMS subscales. However, the strength of the burnout - mood state relationship was inconsistent over the study period. Collectively, these results raise question marks over the use of mood state changes as a marker for burnout in this particular group. Practitioners are, therefore, cautioned against the isolated use of mood state changes as a marker for burnout.