The aim of this study was to assess the reliability and validity of the Questionnaire of Cognitive Schema Activation in Sexual Context (QCSASC; Nobre & Pinto-Gouveia, 2000b). A total of 319 individuals (96 with sexual dysfunctions and 223 without sexual dysfunctions) participated in the study. The QCSASC assesses 28 self-schemas proposed by J. S. Beck (1995), usually associated with psychological problems. The measure assesses the activation of these self-schemas following the presentation of 4 negative sexual events associated with the most common sexual dysfunctions in men and women. The QCSASC demonstrated internal consistency (Cronbach's alpha = .94), test-retest reliability (r[34] = .66), convergent validity (high correlations with other measures of general schemas), and incremental validity. Discriminant analysis differentiated between clinical (sexual dysfunction) and non-clinical groups, giving credit to the hypothesis that the activation of negative schemas may be involved in sexual dysfunctional processes. Findings also suggest the relevance of assessing cognitive schemas in clinical settings.