Genetic explanations of human behaviour are increasingly common. While genetic attributions for behaviour are often considered relevant for assessing blameworthiness, it has not yet been established whether judgements about blameworthiness can themselves impact genetic attributions. Across six studies, participants read about individuals engaging in prosocial or antisocial behaviour, and rated the extent to which they believed that genetics played a role in causing the behaviour. Antisocial behaviour was consistently rated as less genetically influenced than prosocial behaviour. This was true regardless of whether genetic explanations were explicitly provided or refuted. Mediation analyses suggested that this asymmetry may stem from people's motivating desire to hold wrongdoers responsible for their actions. These findings suggest that those who seek to study or make use of genetic explanations' influence on evaluations of, for example, antisocial behaviour should consider whether such explanations are accepted in the first place, given the possibility of motivated causal reasoning.