Abstract: In this study, we evaluated the muscle nutritional quality of Larimichthys polyactis, Larimichthys crocea, and their reciprocal hybrids (L. polyactis ♀ × L. crocea ♂ LPC and L. crocea ♀ × L. polyactis ♂ LCP) by analyzing the biochemical composition and histological structure. The results revealed that the crude fat content of the four yellow croaker populations ranged from 4.73% to 5.37%, classifying them as medium-fat fish. The crude protein content of LPC (16.88%) and LCP (16.93%) exhibited a significant increase compared to both parental lines (16.13% and 16.01%). A total of 17 amino acids, including 7 essential amino acids (EAA), were identified in the four populations. The EAAI varied from 106.69 to 110.42 across different populations. TAA, TEAA, and TDAA levels in LPC and LCP were significantly higher compared to their parental populations. Among the 22 detected fatty acids, DHA and EPA constituted approximately 46.77% to 49.27% of the total PUFA content in all four populations, with significantly higher DHA content observed in both hybrid yellow croaker varieties compared to their parental counterparts. The populations exhibited abundant contents of 4 macroelements (K, Na, Mg, and Ca), while the hybrid yellow croaker species displayed significantly higher levels of Zn and Fe in 6 microelements (Mn, Zn, Fe, Se, Cu, and Cr) compared to their parents. The histological analysis revealed that the muscle fiber density of LPC and LCP was significantly lower compared to that of large yellow croaker, but showed no significant difference when compared to small yellow croaker. Additionally, the muscle fiber diameter of LPC was significantly higher than both parental species. In summary, the muscle nutrients of all four yellow croaker groups were abundant, exhibiting high nutritional value. Furthermore, certain heterosis in specific nutritional indexes was observed in the two hybrid yellow croaker species. These findings explicate the impact of crossbreeding on muscle quality and offer valuable insights for enhancing meat quality and developing new breeds of yellow croaker.