Background Familial risk factors have been implicated in the development of mental health problems in adolescents. Whether the associations between parental loading, as assessed by lifetime psychopathology, and offspring internalising and externalising problems were moderated by family socioeconomic position (SEP) was investigated. Two hypotheses of moderation were tested: (1) the "social push" hypothesis in which parental loading effects are stronger in contexts with low environmental risks and (2) the "vulnerability" hypothesis in which parental loading effects are stronger in high-risk environments. Method In a population-based sample of 2149, familial loading and family SEP were assessed at baseline by parent reports. Offspring psychopathology was assessed by reports from multiple informants (parent, self and teachers). Multiple linear regression was used to assess the independent associations of parental loading and family SEP on offspring psychopathology and their potential interaction. Results Both family SEP and familial loading had significant independent main effects on offspring internalising and externalising problems. However, the interaction terms were not significant and did not add any explanatory power to the model. Conclusions Lower levels of family SEP appear not to confer additional risks for mental health problems in offspring of parents with high loading on psychopathology. During early adolescence, parental psychopathology and low family SEP seem independent risk factors for offspring mental health problems. Results do not support either the social push or vulnerability hypothesis as no evidence of interactions between parental loading and family SEP were found.