Aims: To test if a brief motivational intervention (BMI) in a non-treatment seeking population of heavy drinkers results in a reduced alcohol intake. Methods: Screening of 12,364 participants in a Danish health examination survey led to 1026 heavy drinkers of whom 772 were included and randomized to a BMI group (n = 391) or a control group (n = 381) receiving two leaflets about alcohol. Follow-up took place after 6 and 12 months including 670 and 616 participants respectively. The outcome measure was self-reported weekly alcohol consumption. Data were analysed according to the intention-to-treat principle. We used the Motivational Interviewing Treatment Integrity 3.0 code (MITI) as a quality control of the interventions delivered. Results: The intervention effect of the BMI was −1.0 drinks/week, but the effect was not significant. The MITI analysis showed that the quality of the BMI delivered was sub-optimal, as only one of four aspects was above the recommended level for beginning proficiency. Conclusion: We found no effect of a BMI in reducing alcohol consumption. The generalizability of the study is questionable, as individuals with the lowest level of education, low income and unmarried individuals are under-represented.