Risky sexual behaviour is a major health issue in society, and it is therefore important to understand factors that may predispose individuals to such behaviour. Research suggests a link between risky sexual behaviour and personality, but the basis of this link remains unknown. Hans Eysenck proposed that personality is related to sexual behaviour via biological underpinnings of both. Here we test the viability of this perspective by analysing data from identical and non-identical twins (N = 4,904) who completed a questionnaire assessing sexual attitudes and behaviour as well as personality. Using genetic modelling of the twin data, we found that risky sexual behaviour was significantly positively correlated with Impulsivity (r = .27), Extraversion (r = .24), Psychoticism (r = .20), and Neuroticism (r = .09), and that in each case the correlation was due primarily to overlapping genetic influences. These findings suggest that the genetic influences that shape our personality may also predispose us to risky sexual behaviour.