Self-objectification can be considered as a specific kind of self-dehumanization that consists of a perception of oneself as more instrument-like than human-like and a decreased self-attribution of mental states. Self-objectification is commonly observed, and its contributing factors need to be better understood. In the present research, we examined whether cultural tightness, which entails strong social norms and punishments for deviant behaviors, is an antecedent to self-objectification. Our hypotheses were confirmed by four studies, involving quasi-experiments and fully controlled experiments ( N = 2,693). In particular, Chinese college students living in a region with a tight culture (compared to a loose culture, Study 1), American employees working in an industry with a tight corporate culture (compared to a loose culture, Study 2), American participants who were induced to support cultural tightness (vs. cultural looseness, Study 3), and those who were situated in a simulated tight culture (vs. a loose culture, Study 4) all showed increased levels of self-objectification. As such, they acknowledged their personhood less and focused more on their instrumentality. Implications are discussed.