We develop and validate a measure of entrepreneurship addiction. Inspired by earlier research on entrepreneurship addiction, we develop multi-item scales to measure six underlying criteria (i.e., obsessive thoughts, withdrawal/engagement, self-worth, tolerance, neglect, and negative outcomes). Via three studies, we refine the measure and investigate its dimensional structure. We also provide estimates of prevalence and identify some antecedents of entrepreneurship addiction. The validated measure helps illuminate entrepreneurship addiction’s role in some “dark side” implications of entrepreneurship.