Indoor residual spraying (IRS) is one of the key vector control tools with a long history of use in the world. Ethiopia has set a goal to eliminate malaria from selected districts mainly by applying IRS and the distribution of long-lasting insecticidal nets. IRS is applied in low malaria transmission districts which are epidemic prone and in districts with high malaria transmission. Ethiopia uses insecticides that are recommended by World Health Organization; these insecticides must also be registered in Ethiopia. The registration of new and potential products requires confirmatory, local efficacy trials to be performed. Actellic 300CS, now registered, is one of such potential product. Actellic 300CS showed average mortalities of 99.6%, 99.6%, and 99.0% on the sprayed surfaces in the experimental huts, the top, middle, and bottom sections, respectively during the first 6 mo of the study period. Beyond 6 mo, (7, 8, and 9 mo) follow-up, mortalities for the top, middle, and bottom sections were 85.2%, 86.3%, and 85.2%, respectively. The results showed that the residual efficacy of Actellic 300CS was up to 9 mo with the first 6 mo exhibiting mortalities of greater than 99% while the next 3 mo showed mortalities exceeding 85%. Actellic 300CS was effective against fully susceptible laboratory-reared Anopheles arabiensis on all four surface types (rough, smooth, dung, and painted surfaces) tested in this study and could be used as one of the chemical insecticides of choice for the ongoing IRS programs in Ethiopia.