The quality and quantity of silk produced by the mulberry silkworm, Bombox mori L. are highly influenced by larval feeding, larval ages, care, and types of races. This work investigated effects of adding chamomile and cinnamon oil to larval food on some biological parameters of B. mori. For this purpose, cinnamon and chamomile oils were used in different concentrations (for cinnamon: 0.5 ,0.75, 1%; for chamomile: 1%, 2% and 3%). The results showed that the cinnamon 1% highly increased, in a significant way, the weights of larvae, cocoon and pupae compared with the other concentrations. Further, cinnamon 1% also gave the heaviest weights of larvae and fresh cocoon with an increase of 4.368 and 3.229 g, respectively. In addition, the counts of haemocytes, in general, and especially oenocytoides were higher in those larvae fed on diet containing 1% of cinnamon oil. Furthermore, this concentration increased the immunity of larvae. Furthermore, the best concentration for accelerating the development of B. mori larvae as well as their cocoon weight was found to be 1% of cinnamon oil. From the economical point of view, these results are promising and these oil additives to larval diet could be recommended to improve the sericulture parameters.