The present investigation was conducted to study the effect of fortification of mulberry leaves with different concentrations of baker's yeast Saccharomyces cerevisiae extract and blue-green algae Spirulina platensis extract on some quantitative parameters of Bombyx mori larvae and cocoons. Statistical analysis of the obtained data revealed that all larval treatments showed a significant increase in the larval and cocoon weights, especially at concentrations 0.5 % of yeast and 0.05% of spirulina.Feeding 5^th larval instar with mulberry leaves at concentrations 0.5 % yeast and 0.05% spirulina, lead to increase the larval weight by about 55 % and 30%, respectively, when compared with the control. The same trend was observed in pupal weight, cocoon weight and cocoon shell weight. Larval treatments with yeast extract at concentration 0.5% increased the weights of pupa (0.850 gm), cocoon (0.908 gm) and cocoon shell (0.216 gm) by about 30%, 16% and 27%  as compared with controls which were 0.561gm, 0.781gm and 0.170 gm, respectively. On the other hand,  all larval trials with spirulina extracts remained at the second grade of implementation on the pupal weight, cocoon weight and shell weight. However, feeding B. mori larvae with yeast extract significantly increased the silk ratio and the total haemolymph protein comparing with the spirulina treatments or control ones.