The Islamophobia Scale (IS) is a self-report measure of an individual's fear-related attitudes toward Muslims and the religion of Islam (S. to further validate the psychometric properties of the IS, the current study conducted a confirmatory factor analysis (CFA) and a test-retest reliability analysis (Study 1), a multitrait-multimethod (MTMM) study (Study 2), and an incremental validation study (Study 3). In addition, construct validity was examined across all of the studies using correlations with other instruments. The results demonstrated that the IS is reliable across time, is more factorially sound as a two-factor model, and is correlated with expected instruments. The MTMM demonstrated convergent and discriminant validity, rivaling forgiveness and right-wing authoritarianism (RWA) measures for the cognitive component, but not for the affective-behavioral component. However, the affective-behavioral component explained variance over and above RWA and Arab prejudice measures for sympathetic reactions to a suffering Muslim. Implications, limitations, and opportunities for future research are discussed.