Mental contamination refers to the feeling of being contaminated in the absence of physical contact and can be triggered by immoral behaviour. Differences have been found between victims and perpetrators of immoral behaviour in how much mental contamination they experience. This study aimed to investigate this variability by assessing whether feelings of responsibility could explain the differences found between groups. An online experimental paradigm was conducted where participants (N=121) were asked to recall an autobiographical memory of being either a victim or a perpetrator of immoral behaviour. Mental contamination was measured through participants’ ratings of negative emotions pre and post manipulation. It was found that responsibility was related to mental contamination through ratings of disgust and contamination, but there was no effect of responsibility on group differences when a between groups ANCOVA was conducted. A between groups ANOVA found that victims reported more mental contamination through ratings of anger and the behavioural measure (intention to neutralise). Conversely, perpetrators reported more shame and guilt than victims. These differences suggest that experience of mental contamination is different between groups, with victims having an external negative response and perpetrators reporting more internal negative emotions. These findings are discussed along with potential implications.