BackgroundSexual fantasies and memories are aetiological considerations in the perpetration of sexual violence, but fantasy–memory–behaviour relationships may be influenced by various factors, including sexual fantasy and memory phenomenology, that are the properties of mental imagery.AimsTo investigate differences in sexual fantasy phenomenology and sexual memory intensity in men who report a history of harmful sexual behaviour compared to those who do not. We also investigated whether the likelihood of reporting harmful sexual intent was related to sexual memory intensity, independently of age and harmful sexual behaviour history.MethodsAn online cross‐sectional survey design was used, focusing on men aged ≥18 years who were recruited from the general population via social media. The survey prompted participants to envisage a favoured sexual fantasy, then obtained data on fantasy phenomenology, including vividness and sensations, and arousal level. In addition, information was requested about sexual memory intensity and harmful sexual behaviour history and intent.ResultsA total of 322 men completed the survey. Multiple Welch's t‐tests showed that men self‐reporting one or more harmful sexual behaviours, such as rape or child sexual abuse, gave significantly higher ratings of sexual fantasy phenomenology but not fantasy frequency or masturbation. They were also more likely to report higher sexual memory intensity. Although the significance of fantasy phenomenology varied between subgroups, binary logistic regression indicated that age, history of harmful sexual behaviour and sexual memory intensity were each independently associated with harmful sexual intent.ConclusionsOur findings provide new insights into the importance of fantasy phenomenology, demonstrating nuanced differences between those with and without a history of harmful sexual behaviour and illustrating that memory intensity is associated with harmful sexual behaviour intent. Further research into these differences in the context of assessment and intervention for sexual violence perpetration is warranted.