INTRODUCTION AND AIMS: Alcohol use during adolescence is associated with the onset of alcohol use disorders, mental health disorders, substance abuse as well as socially and physically damaging behaviours, the effects of which last well into adulthood. Nevertheless, alcohol use remains prevalent in this population. Understanding motivations behind adolescent alcohol consumption may help in developing more appropriate and effective interventions. This study aims to increase this understanding by exploring the temporal relationship between mood and different levels of alcohol intake in a sample of young people. DESIGN AND METHODS: Forty-one secondary school students used a purpose-designed mobile phone application to monitor their daily mood and alcohol use for 20 random days within a 31 day period. Generalised estimating equations were used to examine the relationship between differing levels of alcohol consumption (light, intermediate and heavy) and positive and negative mood three days before and after drinking episodes. RESULTS: While there was no relationship between light and heavy drinking and positive mood, there was an increase in positive mood before and after the drinking event for those that drank intermediate amounts. No statistically significant relationships were found between negative mood and any of the three drinking categories. DISCUSSION AND CONCLUSION: Adolescents who drank in intermediate amounts on a single drinking occasion experienced an increase in positive mood over the three days leading up to and three days following a drinking event. These findings contribute to an understanding of the motivations that underpin adolescent alcohol use, which may help inform future interventions.