Mental contamination refers to feelings of dirtiness and/or urges to wash that arise without direct contact with a contaminant. Cognitive models propose that this results from "serious, negative misappraisals of perceived violations". However, the specific violation misappraisals most relevant to mental contamination have yet to be established empirically, in part due to the lack of a comprehensive validated inventory of violation appraisals. Therefore, this study's aim was to develop and validate such a measure. Items for the new Violation Appraisal Measure (VAM) were developed from qualitative interviews, theoretical models, and previous empirical work. An Exploratory Factor Analysis was conducted in a sample of (n = 300) undergraduate participants, which revealed a four-factor structure: Responsibility/Self-Blame, Permanence, Mistrust, and Self-Worth. The VAM showed excellent internal consistency ($\alpha$ = 0.90), good convergent (r = .50 to .64) and adequate divergent (r = -.01 to .46) validity and was predictive of mental contamination symptoms over and above existing related appraisal measures, $\Delta$F(1,289) = 29.35, p < .001, $\Delta$R² = 0.06. A Confirmatory Factor Analysis in a second sample of (n = 300) undergraduate students confirmed strong model fit for the four-factor structure of the VAM. The development of the VAM is an important contribution to the search for empirically based cognitive mechanisms in mental contamination and other violation-related sequelae.