Abstract: Background: Tropical tasar silkworm, Antheraea mylitta Drury (Lepidoptera: Saturniidae) is a polyphagous sericigenous insect, producing tasar silk of high commercial value. Generally, rearing of tasar silkworm (DABA ecorace) is conducted two to three times in a year. During second and third crop rearing sometimes during low temperature regimes cause prolongation of larval duration which causes unsynchronized cocoon-spinning leading to decreased production and productivity. Methodology: In the present study, impact of exogenous application of phyto-ecdysteroids has been evaluated on growth, development, moulting, spinning and cocoon-spinning synchronisation pattern of tasar silkworm A. mylitta. Results: The highest percentage of cocoon spinning was observed with treatment T5 (Sampoorna) which was followed by T4 (Vitex negundo). Although the cocoon weight, shell weight and silk ratio of treated and control lots were not varied significantly, marked improvement in cocoon-spinning synchronisation was observed when phyto-ecdysteroid T1 (Achyranthus aspera) and T5 (Sampoorna) treatment. Conclusion: It is expected that, an application of a refined dose of phyto-ecdysteroid will synchronise the spinning for enhanced production and productivity of the silkworm, A. mylitta.