This study aimed to quantify correlations between theory of planned behaviour (TPB) variables and (i) intentions to consume alcohol and (ii) alcohol consumption. Systematic literature searches identified 40 eligible studies that were meta-analysed. Three moderator analyses were conducted: pattern of consumption, gender of participants and age of participants. Across studies, intentions had the strongest relationship with attitudes (r + = .62), followed by subjective norms (r + = .47) and perceived behavioural control (PBC; r + = .31). Self-efficacy (SE) had a stronger relationship with intentions (r + = .48) compared with perceived control (PC; r + = −.10). Intention had the strongest relationship with alcohol consumption (r + = .54), followed by SE (r + = .41). In contrast, PBC and PC had negative relationships with alcohol consumption (r + = −.05 and −.13, respectively). All moderators affected TPB relationships. Patterns of consumption with clear definitions had stronger TPB relations, females reported stronger attitude–intention relations than males, and adults reported stronger attitude–intention and SE–intention relations than adolescents. Recommendations for future research include targeting attitudes and intentions in interventions to reduce alcohol consumption, using clear definitions of alcohol consumption in TPB items to improve prediction and assessing SE when investigating risk behaviours.