Worldwide Aedes aegypti is the principal urban vector of several major human pathogens, including dengue, Zika, chikungunya and yellow fever viruses. In Mexico, control of this mosquito strongly relies on the use of pyrethroids against adults and larvae. In consequence, many Ae. aegypti field populations have become resistant to insecticides. Pyrethroids kill mosquitoes by binding to the voltage gated sodium channel (VGSC) and preventing its proper functioning. Resistance to pyrethroids arises through nonsynonymous mutations in the VGSC gene that reduce pyrethroid binding, known as knockdown resistance (kdr). The insecticide resistance mutations have been shown to have a large fitness benefit in the presence of insecticide treatment. However, in the absence of insecticide, there is frequently reported reduced frequency of the mutant allele which suggests the mutation has a fitness cost. We evaluated the fitness cost of some kdr mutations on several life-history parameters as well as common abiotic stresses faced in the field. Specifically, we compared 2 populations differing in the frequency of the kdr mutations but otherwise of identical genetic background and we found a significant difference between the resistant and susceptible strains in adult dry mass upon emergence, adult water reserves, adult lipid reserves, and larval thermal tolerance. In contrast, both strains responded similarly to larval salinity stress and adult desiccation stress. Our results suggest that these Ae. aegypti kdr mutations indeed have some fitness cost, whether directly or indirectly associated with them. This is critical to determining the extent to which insecticide resistance interacts with life history traits and should provide key information for vector control in the future.