Information is a core input of governance that is often disrupted by the processes associated with globalization. To mitigate potential governance failures, states turn to information sharing – the exchange of sensitive data between governments. Such exchanges, however, come with considerable risks. Building on work in International Relations and organizational sociology stressing the importance of institutional similarity, we argue that states commit to information sharing based on their beliefs as to the reliability and predictability of potential partners – an assessment that involves a relative evaluation of domestic institutions. We test our argument on institutional similarity with a new dataset of mutual legal assistance treaties (MLATs) – a critical example of information-sharing agreements. The empirical analysis finds substantial support for our argument: states with similar legal institutions are much more likely to sign MLATs. The article contributes to a range of research concerned with the politics of globalization, especially as it relates to enforcement cooperation, the role of domestic institutions, and information flows.