In a meta-analysis of research on measures of the habit construct, we aimed to estimate the size and variability of habit–behavior and intention–behavior relations, and habit as a mediator of past–future behavior relations. Furthermore, we investigated the theory-consistent moderators of these relations including opportunity for habit formation and behavioral complexity, and the capacity of different habit measures to detect these effects. We also tested effects of behavior type, behavior measure, and measurement lag as moderators of these effects, and explored convergence in correlations among habit measures and their indication of a single habit factor. A database search identified studies (k = 267) reporting relations among habit measures (behavioral frequency × context stability, response frequency, self-report measures), behavior, and intention. Data were analyzed using multilevel meta-analytic structural equation modeling. Habit and intention independently predicted behavior, and habit partially mediated past–future behavior relations. Larger habit–behavior relations were observed in studies targeting behaviors with high opportunity for habit formation and lower complexity, but no analogous effects for intention–behavior relations. Similar trends for these moderators were observed across the habit measures, although differences were nonzero for self-reported habit measures only. Habit–behavior relations were larger in studies adopting self-report habit measures that included behavioral frequency items and those with greater measurement lag. Convergence in habit measure correlations, and their indication of a single habit factor, was supported. Findings corroborate and extend prior research on habit, particularly convergence in behavioral effects of the habit measures. Findings are expected to catalyze future habit research using experimental methods and non-self-report measures. (PsycInfo Database Record (c) 2023 APA, all rights reserved)