The predaceous Coccinellids are major taxa for inoculative and inundative biological control programs and studying fitness of both the female and the male allow us to know more about their efficacy. The diet quality have critical role in Coccinellids' fitness. Since the natural diets are greatly used for marketing rearing of Coccinellids, here, the effect of the plant nutritional levels on the fitness of its male and female was addressed. Crop nitrogen fertilization is of a typical agricultural practice which by changing plant nutritional level would strikingly alter nutritional quality of herbivore. As recently shown, macronutrients in prey is primary determinant influencing predator efficacy. So, the effect of three nitrogen (N) diets, the sub-optimal (110 ppm), optimal (160 ppm) and super-optimal (210 ppm), on the female reproduction potential and both the female and the male longevity of Hippodamia variegata reared on Aphis gossypii cultured on the cucumber was studied. The results illustrated that the aphids reared on the treatment 210 had the highest nutritional level (total macronutrients = 74.2 ± 8.5, protein = 17 ± 3.5), however, the beetle females in the treatment 210 did not had the greatest the intrinsic rate of increase (rm) (0.176 ± 0.016) and the maximum rm was observed in beetles fed on the 160-reared aphids (0.187 ± 0.007) who had the middle quality (65 ±5, 12.5 ± 2). As decreasing prey quality through treatments, female longevity improved and was the greatest in females in the treatment 110, indicating low prey quality led to low reproduction in the 110-fed females in which energy needed for more lifespan of females was provided to probably meet good nutritional condition for high reproduction at future. Indeed, the nutritional diet trades off between longevity and reproduction in the females. The 160-fed males longer lived than those in other treatments and there was not the reverse relationship between prey quality and male longevity; because successful fitness in males is related to more successful sexual activities at which more carbohydrate resources is needed. In treatment 160, the nutritional condition for high fitness of males was more provided.