Anthropogenic climate change is an existential threat to both humans and wider biodiversity. However, cumulatively, individuals’ actions can help to mitigate the impacts of climate change. Understanding the factors which shape individuals’ beliefs about climate change, and their environmental behaviours, is therefore crucial. Here, we explore whether individual differences—Big-5 personality traits and cognitive ability—are associated with climate beliefs and behaviours, using longitudinal data from a UK birth cohort study. Individual differences were measured when the participants were teenagers (aged 13 to 15 years), with climate beliefs and behaviours assessed at approximately age 30 years. These climate beliefs and behaviours included: belief that the climate is changing, concern over climate change, whether humans are to blame for climate change, whether individual actions can mitigate climate change, and whether they were undertaking a range of pro-environmental behaviours for climate reasons (e.g., reducing air travel, reducing meat/dairy consumption). Regression models were used to explore the associations between individual differences and climate belief and behaviour outcomes, adjusting for a range of relevant sociodemographic confounders. Overall, we found consistent positive associations between agreeableness, openness to experience and cognitive ability scores and environmental knowledge and action. Weaker, and more inconsistent, associations were reported for extraversion, conscientiousness and emotional stability. These results suggest that individual differences may shape an individual’s beliefs and actions regarding climate change, and potentially indicates groups where climate information campaigns could be targeted.