Why, how, and under what conditions do moral beliefs persist despite institutional pressure for change? Why do the powerful often fail to promote the morality of their authority? This paper addresses these questions by presenting the role of crypto-morality in moral persistence. Crypto-morality is the secret adherence to one morality while practicing another in public. A simple overlapping generations model is developed to examine the conditions under which crypto-morality is practiced, decays and influences the direction of moral change. We demonstrate the empirical relevance of crypto-morality by discussing the moral foundations of political legitimacy in various historical episodes.