The grandchildren of immigrants have long been regarded as a litmus test for whether immigrant-origin populations successfully incorporate into the destination societies. Yet, we know very little about the ’new’ third generation—that is, the grandchildren of immigrants who immigrated in the postwar era to Europe. Here, we rely on new, large-scale French data providing a unique opportunity to study the socioeconomic attainment of third-generation individuals in adulthood compared with the second generation and French natives. We jointly analyze educational and labor market attainment using five indicators at both the top and bottom of the distributions, leading to a comprehensive understanding of immigrant incorporation across generations. We report three major results. First, we find a master trend across groups and outcomes reflecting parity with natives, often already achieved at the second generation. Second, third-generation attainment is moderated by gender and national origins: we document lasting educational disadvantages for North African, third-generation males, while Southern Europeans are more likely to experience economic incorporation within the lower class. Third, mixed ancestry ceases to positively predict socioeconomic attainment by the third generation. These results have important implications for ongoing scholarly discussion of immigrant incorporation in France and beyond.