Perceiving work as a calling has been positioned as a key pathway to enhancing work-related well-being. However, no formal theory exists attempting to explain predictors and outcomes of living a calling at work. To address this important gap, this article introduces a theoretical, empirically testable model of work as a calling - the Work as Calling Theory (WCT) - that is suitable for the contemporary world of work. Drawing from research and theory in counseling, vocational, multicultural, and industrial-organizational psychology, as well as dozens of quantitative and qualitative studies on calling, the WCT is presented in three parts: (a) predictors of living a calling, (b) variables that moderate and mediate the relation of perceiving a calling to living a calling, and (c) positive (job satisfaction, job performance) and potentially negative (burnout, workaholism, exploitation) outcomes that result from living a calling. Finally, practical implications are suggested for counselors and managers, who respectively may seek to help clients and employees live a calling.