This paper studies the relation between party institutionalization and intra-party preference homogeneity in democracies. In weakly institutionalized parties, it cannot be taken for granted that party actors have similar policy views because they lack the capability or motivation to coordinate agreement and to recruit personnel in line with this agreement. This should matter most when other safeguards against preference heterogeneity are missing. Empirically, we explore the association between institutionalization and intra-party preference homogeneity at the level of candidates to the national legislature based on survey data. In a single-country study, we first look at the case of Germany in 2013 and 2017, contrasting the young and weakly institutionalized Alternative for Germany (AfD) with the older, established parties. In a second step, we study the link between party institutionalization and preference homogeneity in a cross-country analysis of 19 established democracies. We find that parties with high value infusion—parties whose candidates are committed to the party—are generally more homogenous in their policy preferences. Moreover, value infusion is more consequential when the issues in question are not constitutive for the party and when candidates are selected in a decentralized way. Similarly, routinization of internal party behavior—the second dimension of institutionalization that we account for—seems to contribute to preference homogeneity only when parties are less policy oriented and have decentralized candidate selection procedures.