© 2018 Elsevier Inc. Improving sexual and reproductive health remains a public health priority worldwide. This study explored the contribution of personality to adolescent sexual behaviour. In total, 3460 Australian adolescents (1748 boys, 1712 girls) were sampled at age 12 and age 14. Results showed that mean-level increases in neuroticism and extraversion, and mean-level decreases in conscientiousness, were associated with an increased likelihood of being sexually active at age 14. Mean-level increases in neuroticism (and for girls, lower levels of conscientiousness) were associated with an increased likelihood of same-sex sexual attraction at age 14. Intra-individual stability of extraversion was related to the number of adolescent relationships and same-sex sexual attraction. Sexual risk taking and pregnancy were too rare at age 14 to reliably explore correlates.