Background and aims: The influence parental drinking on offspring's drinking is well-documented. However, longitudinal evidence on the mediating role of drinking motives in this relationship is lacking. This study longitudinally investigates the mediating role of drinking motives in the relationship between parental and offspring's drinking. Methods: Using a prospective design, 587 Flemish children (response 30.0%) were followed for 9 years. Parental drinking was documented during the offspring's late childhood (10 and 11 years old) through paper-and-pencil questionnaires distributed by schools. The offspring's drinking habits and -motives were documented in early adulthood (18 and 19 year old) through a web-based questionnaire; invitations were sent by letter. Motives were measured using the Drinking Motives Questionnaire Revised Short-form, and mediation analyses were conducted with the product of coefficient test using bootstrapping. Results: Half the offspring were female (53.8%) and the mean age was 19.35 (SD=0.52) years. A significant direct effect of maternal drinking during childhood on offspring drinking nine years later was found beta=0.091, t=2.071, p=0.039). However, the association turned non-significant after stratifying the model for boys and girls. No direct effect was found for paternal drinking on offspring's drinking. Nevertheless, paternal drinking indirectly affected offspring's drinking through offspring's enhancement motives (beta=0.041, 95%CI[0.004, 0.082]) and maternal drinking indirectly affected male offspring's drinking through offspring's social motives (beta=0.067, 95%CI[0.007, 0.148]). Conclusion: These results show that parental drinking during late childhood relates to a high level of those drinking motives among young adults that are known risk factors for heavy drinking in early adulthood.