Background The impact of staff and service user gender on responses of staff in intellectual disability (ID) services is poorly understood. The present study set out to assess the role of gender in influencing staff emotions, attributions and behavioural intentions in response to aggression displayed by adults with ID. Method A new scale measuring staff behavioural intentions was developed. A two × two (staff gender × service user gender) between subjects design was used to compare the responses of day and residential support staff to physical aggression by a hypothetical service user. In response to a vignette depicting a service user with ID assaulting a member of staff, 160 respondents completed measures of affective responses, causal attributions and behavioural intentions while imagining themselves as the target of the service user's assault. Results Female participants reported feeling more fear/anxiety, more depression/anger and less confident/relaxed than male participants. The longer staff had worked with people with ID, the more likely they were to favour safety‐focused behaviours. More confident female participants were less likely to favour safety‐focused behaviours, but confidence had no effect on male participants' endorsement of these behaviours. Increased confidence in both was associated with lower agreement of safety‐focused behaviours in relation to the female vignette, regardless of participant gender. The more control women believed the service user had over their behaviour, the more likely they were to choose safety‐focused behaviours. Punitive behaviours were favoured more in response to the male rather than the female service user. Punitive behaviours were also favoured more by more junior staff and by participants who expected feeling more depressed/angry in response to the vignettes. Conclusions Both staff and service user gender influenced staff responses to aggression, yet the latter played a smaller role than expected. The role of gender in staff–service user interactions should be the focus of further research and should be considered in service delivery.