The increasing pluralism of modern workplaces has foregrounded the urgent need for tools that assess and strengthen religious inclusion. While diversity, equity, and inclusion (DEI) frameworks have expanded worldwide, faith inclusion remains an underexplored dimension, often resulting in spiritual marginalization or identity?based microaggressions in professional environments. This study introduces the Faith-Inclusivity Index (FII), a psychometrically validated instrument designed to measure faith-inclusion climates across diverse organizational settings. Using an exploratory sequential mixed-methods design consisting of expert consultations, item generation, content validation, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), the final FII includes seven subscales capturing policy, structural, perceptual, and interpersonal dimensions of faith inclusion. A pilot study (N = 210) and full validation study (N = 510) demonstrate high reliability (Cronbach’s α = .91) and good construct validity (CFI = .94; RMSEA = .052). The study concludes that FII is a globally applicable tool offering significant utility for scholars, HR leaders, and policymakers aiming to create faith-inclusive workplaces. Recommendations for practice, implications for global DEI, and future research directions are discussed.