The present investigation was conducted to assess the effect of different dietary protein percentages and starvation on the health, behavior, blood chemistry, immune response and histoarchitectures of fan tail gold fish Carassius auratus L. Experiment was carried out using 80 Carassius auratus with an average body weight 18±2 g which were divided into four groups in duplicate in which, group 1 feed with diet A; 28% Crude Protein (CP). Fish in group 2 was fed on diet B (17% CP) and fish in group 3 was feed on diet C (45% CP) and group 4 kept as fasted group. The experimental period was 8 weeks. The current study clarified that significant high growth rate, improved welfare, decrease aggressive behavior, improved biochemical serum parameters and immune response were observed in group feed with diet containing 45% crude protein. Starvation is directly affect health, immunity and welfare as well as histoarchitectures of all selected organs. Histologically, there is no any significant changes on the histoarchitectures of the all selected organs; liver, spleen, intestine, head kidney as well as muscle of groups 1, 2 and 3 feed with diet A (28% CP), diet B (17% CP) and diet C (45% CP) respectively. Meanwhile, the fasting of group 4 had the most effective changes on the histoarchitectures of all selected organs.