In Pakistan, the aquaculture industry is still in its early stages, and no significant work has been reported in crab aquaculture. A few local fishermen are practicing non-scientific farming of mud crabs, using naturally available feed. This study was conducted to initiate crab fattening practices along the coastal regions of Pakistan; for this purpose, Portunid crabs (Scylla serrata) were selected due to their muddy bottom habitat. The experiment was designed in which two groups of crabs (S.serrata), designated Group A and Group B, were fed different diets, and their body tissues were analyzed using biochemical techniques. Group A was given a natural diet (trash fish), while Group B received a formulated feed. Biochemical analysis of Group A’s tissues revealed that protein content (20.82±0.98 mg/g) was higher than lipid (0.49±0.34 mg/g) and carbohydrate (1.02±0.16 mg/g) levels. Similarly, the analysis of Group B indicated that protein levels (19.47±2.00 mg/g) were higher than lipids (0.72±0.25 mg/g) and carbohydrates (1.17±0.32 mg/g). The biochemical comparison of both groups showed that Group A had a higher protein content, while Group B had higher lipid and carbohydrate levels. Growth assessment parameters such as feed conversion ratio (FCR), carapace length (CL), carapace width (CW), and mass increment were better in Group A, which was fed a natural diet. However, the survival rate (SR) was higher in Group B, which received the formulated feed. It was concluded that continuous research is required to improve feed formulation to enhance the growth of crabs and build the aquaculture industry in Pakistan.