Objectives: The longitudinal relationship of mental health, alcohol consumption, and their direction of effect are not well understood, and findings are mostly heterogeneous. The study investigates the mutual effects of mental health and alcohol consumption over time in a general population sample. Methods: Self-report data of n = 816 adults aged 18–64 who reported any alcohol consumption in the past year (57.5 % female) were used. Participants were proactively recruited at a municipal registry office and provided data at 4 measure points (baseline, 3, 6, and 12 months). Mental health was assessed using the 5-Item Mental Health Inventory. Alcohol consumption was measured as the number of drinks in the last 30 days using a quantity-frequency index. Bivariate latent change score models with different assumptions were estimated in four models: 1) alcohol consumption and mental health trajectories did not influence each other, 2) alcohol consumption influenced changes in mental health, 3) vice versa, and (4) a reciprocal model in which both influenced changes in each other. Results: The third unidirectional coupling model fitted the data best (Chi-square (24) = 107.78, p < .01, CFI = 0.96 RMSEA = 0.06, SRMR = 0.03). Better mental health at earlier assessments was associated with lower alcohol consumption in future, but not vice versa. Conclusions: The results that, among a general population sample of persons who reported any alcohol consumption, higher levels of mental health may spill over and lead to a decrease in monthly alcohol consumption.