Collegiality plays a central role in judicial decision-making. However, we still lack empirical evidence about the effects of collegiality on judicial decision-making. In this article, I argue familiarity, an antecedent to collegiality, improves judicial deliberations by encouraging minority dissent and a more extensive debate of different legal viewpoints. Relying on a novel dataset of 21,613 appeals in criminal cases at the German Federal Court of Justice between 1990 and 2016, I exploit quasi-random assignment of cases to decision-making groups to show that judges' pairwise familiarity substantially increases the probability that judges schedule a main hearing after first-stage deliberations. Group familiarity also increases the length of the justification of the ruling. The findings have implications for the way courts organize the assignment of judges to panels.