This study was undertaken to evaluate the effect of larval diet Rastrineobola argentae on pupae eclosion and mating success of adult Anopheles arabiensis Patton (Diptera: Culicidae). Rastrineobola argentae as a test diet and Tetramin^® Baby as a comparative diet were fed to An. arabiensis larvae to generate adults raised exclusively on either of the two diets. Early pupae raised on the diets were placed in containers measuring 6 cm × 5.7 cm × 3.5 cm and assessed for pupae eclosion success. Emerged adults were sexed, transferred to holding cages and provided with 10% sugar solution. Ten three day old virgin male and female raised either on same or different diet types were paired in similar containers as pupae, given 10% sugar solution and left to mate. A wing was removed from experimental mosquitoes and measured to determine size. Spermathecae from every female was removed and examined for sperms. Diet type did not influence pupae eclosion success. Highest proportion of emerged (56%) and competitive (78%) males were associated with crushed silver cyprinid fish food. Female mosquito size influenced mating success (p=0.008) for Tetramin^® Baby fish food raised mosquitoes and not crushed silver cyprinid fish (p=0.068) raised mosquitoes. Most females inseminated were raised from the same diet as the males. Diet type influenced mating success and size. High proportions of larger females were inseminated compared to smaller ones.