The amount of sperm and secretions from the male accessory glands that are transported to the paired females during mating determines the reproductive success of animals. Three sympatric species of Drosophila, including D. malerkotliana, D. bipectinata, and D. nasuta, were collected from Chamundi Hill for this study on the effects of altitude on accessory gland features and sperms transmitted by male to female during copulation and its consequences on fitness. Unmated males of all three sympatric species of Drosophila in low altitude were found to have much more larger major cells in their accessory glands, as well as a larger accessory gland and more accessory gland protein. They had longer copulations yet took less time to mate. Furthermore, compared to flies acquired from either moderate or high elevations, these ones were better able to transport more sperm and accessory gland proteins to mated females, as well as generate more eggs and offspring. In addition, among the three sympatric species, D. malertotliana considerably outproduced D. bipectinata and D. nasuta in terms of the amount of accessory gland proteins and sperm transported to mated females. Three species' subsequent reproductive success was in the following order: D. malertotliana>D. bipectinata>D. nasuta. Therefore, these investigations imply that in all three sympatric species of Drosophila, low altitude flies had higher reproductive success than those at intermediate and high elevations. Compared to D.bipectinata and D.nasuta, D.malerkotliana showed much better reproductive success