Dengue fever (DF) is a viral disease caused by the dengue virus, which is transmitted by the mosquitoe Aedes aegypti and endemic in some cities of Saudi Arabia, such as Jazan area. And because of the toxicity of the chemical- insecticides used in pest control programs, therefore, there is a need to use effective and safe alternative methods to eliminate pests. Therefore, the current study aimed to use the bacterium Bacillus thuringiensis as a biocide against the larval stages of Ades aegypti. Bacillus thuringiensis var. israelensis was applied in two formulations, (water-dispersible powder and Liquid formulation), were examined for their toxicity against immature and adult stages of Ades aegypti in the laboratory. Results indicated that the 50 % lethal concentration (colony forming unit, CFU) of B.t.israelensis against 4th instars, was 8.31x105 CFU mL-1 in liquid formulation and 6.72 x105 CFU gm-1 for wettable powder. Bioassay data also showed that pupation percent and adult emergence were affected more by subjecting the larvae to wettable powder than liquid formulation. The mortality values for the adults ranged between 49.33 & 64.23 % when using liquid formulation and wettable powder, respectively.