Modesty carries important values across both Eastern and Western cultures. Based on an extensive review on existing modesty accounts and research, two types of modesty ----“authentic modesty” (AM) and “tactical modesty” (TM) ---- were proposed and distinguished. Authentic modesty, as a kind of manifestation of authentic self, is based on personalized modesty values or beliefs. In contrast, tactical modesty, as a response to situational requirements, is independent of one’s personalized values or beliefs. Four studies, consisting of nine sub-studies in total, were conducted to identify the features and functions of authentic modesty and tactic modesty. Study 1 explored prototype of AM and TM. Based on findings of Study 1, an Authentic Modesty and Tactical Modesty Scale (AM&TM Scale) was developed, with desirable reliability and construct validity. Study 3 showed that AM and TM were differentially associated with psychological well-being: AM was a strong predictor of well-being, while the relation between TM and well-being was inconsistent and contingent on specific psychological and physical facets. Study 4 explored how AM and TM moderated self-evaluation in different social contexts (private vs. public), and showed that, for people with high AM, self-evaluation did not vary with situation,while people with high TM adopted different self-expression strategies in different situations. Together, these findings suggest that AM and TM have differential contents, adaptive functions and sensitivities to situational variation: individuals with high authentic modesty goes with a quiet and stable ego, cope with stresses actively, and experience more positive affects and less negative affects; individuals with high tactical modesty are sensitive to environmental changes, cope with stress passively or negatively, and experience more negative affects but less positive affects. This research deepens the understanding of modesty and offers a new theoretical foundation for the practice of modesty in modern society.