BACKGROUND: Energy drinks are widely consumed, and concerns have been raised about possible negative outcomes. AIMS: The aim of the present research was to examine associations between consumption of energy drinks, caffeine and junk food, and academic attainment in a sample of UK secondary school students. METHODS: A total of 3071 students agreed to participate in the study; 2677 completed the survey on one occasion (52.4% female, 47.6% male; approximately 20% of the sample from each school year) and 1660 (49.6% female, 50.4% male) completed the survey a second time, approximately six months later. The academic attainment measure was based on Key Stage 3 and Key Stage 4 grades for Maths and English. RESULTS: In the cross-sectional analyses, logistic regressions showed that consumption of energy drinks was associated with a greater likelihood of being in the low academic achievement group. This was not found for other sources of caffeine. The effect of energy drinks was still significant when demographic, academic and health/lifestyle variables were covaried. However, inclusion of an unhealthy diet variable (junk food) removed the significant effect of energy drinks. Similar observations were made in the longitudinal study, with the poorer attainment of those who consumed energy drinks reflecting breakfast omission and depression. DISCUSSION: The present findings indicate that consumption of energy drinks is associated with an increased likelihood of poor academic attainment that reflects energy drink consumption being part of an unhealthy diet or being associated with skipping breakfast rather than a more specific effect, such as being a source of caffeine. Although the current study extends previous research by utilising a longitudinal design, intervention studies are now required to better answer questions relating to causality and direction of effect.