BACKGROUND: Intention is theorized as the proximal determinant of behavior in many leading theories and yet intention-behavior discordance is prevalent. PURPOSE: To theme and appraise the variables that have been evaluated as potential moderators of the intention-physical activity (I-PA) relationship using the capability-opportunity-motivation- behavior model as an organizational frame. METHODS: Literature searches were concluded in August 2020 using seven common databases. Eligible studies were selected from English language peer-reviewed journals and had to report an empirical test of moderation of I-PA with a third variable. Findings were grouped by the moderator variable for the main analysis, and population sample, study design, type of PA, and study quality were explored in subanalyses. RESULTS: The search yielded 1,197 hits, which was reduced to 129 independent studies (138 independent samples) of primarily moderate quality after screening for eligibility criteria. Moderators of the I-PA relationship were present among select variables within sociodemographic (employment status) and personality (conscientiousness) categories. Physical capability, and social and environmental opportunity did not show evidence of interacting with I-PA relations, while psychological capability had inconclusive findings. By contrast, key factors underlying reflective (intention stability, intention commitment, low goal conflict, affective attitude, anticipated regret, perceived behavioral control/self-efficacy) and automatic (identity) motivation were moderators of I-PA relations. Findings were generally invariant to study characteristics. CONCLUSIONS: Traditional intention theories may need to better account for key I-PA moderators. Action control theories that include these moderators may identify individuals at risk for not realizing their PA intentions. Prospero # CRD42020142629.