Background: Long lasting insecticide treated nets (LLINs) and indoor residual spraying (IRS) are interventions commonly used in most malaria endemic areas. Development of insecticide resistance among malaria vector species to commonly used insecticides has increased need for developing new and alternative chemicals to manage the spread of insecticide resistance. In the present study, chlorfenapyr indoor residual spraying was evaluated against wild Anopheles arabiensis and Culex quinquefasciatus. Methods: Chlorfenapyr IRS and residual activity assessment were evaluated in experimental huts against wild Anopheles arabiensis and Culex quinquefasciatus in Moshi Northern Tanzania, at 250mg/m2. Walls and ceilings in trial huts were plastered with concrete and left for 6 weeks to cure before spraying. Insecticides were sprayed using Hudson X-pert compression. Results: Mortality rates in An. arabiensis and Cx. quinquefasciatus were 55% and 15% respectively with chlorfenapyr, which were lower than alphacypermethrin 84% and 33% respectively. Blood feeding rates of An. arabiensis were high across all treatments (70%-74%). CFP provided comparable protection against blood feeding An. arabiensis to alphacypermethrin and CFP-alphacyepermethrin mixture (p>0.05). Chlorfenapyr IRS on concrete walls was found to be effective up to 4 months against An. arabiensis. Conclusion: Mortality in chlorfenapyr sprayed hut was higher as compared to the findings from the study which ceiling was not sprayed indicating that ceiling spraying improves the efficacy of an insecticide. Also findings from this study indicated that Chlorfenapyr-alphacypermethrin mixture can also be used in vector control. CFP residual activity rages at 4-5 months which is can be used in interrupting malaria transmission in endemic areas. Keywords: Indoor residual spraying, Chlorfenapyr, Anopheles arabiensis, Culex quinquefasciatus, experimental hut