Background Mental contamination (MC) describes subjective internal feelings of ‘dirtiness’ which are experienced in the absence of direct physical contact/contaminants. There is evidence of a link between MC in Obsessive Compulsive Disorder (OCD) and the experience of past betrayals. However, the role of the perception that one might betray others is unclear. Aims This study aimed to replicate the previous finding of specificity of OCD for sensitivity to being betrayed, and to determine whether people with high MC OCD are also relatively more sensitive to the idea that they might betray others compared to those with low levels of MC OCD. The study also aimed to investigate the role of rumination and responsibility in MC. Method A cross-sectional, between-groups design was used. Four groups, high MC OCD (N= 60), low MC OCD (N=61), depression (N=28) and non-clinical controls (N=46) completed a series of measures via an online questionnaire. Participants were recruited through the National Health Service(NHS) and social media platforms. Results Relative to all groups including low MCOCD participants, the high MC OCD group had significantly higher scores both for betrayal sensitivity and sensitivity to betraying others. The depression group showed similar levels to low MC OCD in betrayal sensitivity but were significantly lower (and comparable to non-clinical controls) in terms of sensitivity to betraying others. Rumination and responsibility were both found to be associated with MC. Conclusions Betrayal appears to be an important construct for people with high MCOCD, and possibly general psychopathology as demonstrated by the depression group scores. There appears to be a specific link between high MC OCD and the perception of betraying others.