Personality is a relevant predictor for important life outcomes across the entire lifespan. Although previous studies have suggested the comparability of the measurement of the Big Five personality traits across adulthood, the generalizability to childhood is largely unknown. The present study investigated the structure of the Big Five personality traits assessed with the Big Five Inventory-SOEP Version (BFI-S; SOEP = Socio-Economic Panel) across a broad age range spanning 11–84 years. We used two samples of N = 1,090 children (52% female, Mage = 11.87) and N = 18,789 adults (53% female, Mage = 51.09), estimating a multigroup CFA analysis across four age groups (late childhood: 11–14 years; early adulthood: 17–30 years; middle adulthood: 31–60 years; late adulthood: 61–84 years). Our results indicated the comparability of the personality trait metric in terms of general factor structure, loading patterns, and the majority of intercepts across all age groups. Therefore, the findings suggest both a reliable assessment of the Big Five personality traits with the BFI-S even in late childhood and a vastly comparable metric across age groups.