Aims: To assess the toxic potential of different local Jordanian Bacillus thuringiensis isolates on larvae of Drosophila melanogaster and Culex sp. Methods and Results: Scanning electron microscopy revealed the presence of spherical, bi-pyramidal, and bi-pyramidal and cuboidal parasporal bodies produced by the toxic isolates. Spherical inclusions dominated. The toxicity of the isolates to the two insects, determined using 24-well plates or vials, indicated that the 50% lethal concentration (LC50) of the bacterial suspension for D. melanogaster and Culex sp, larvae varied from 4.60 to 8.65 and from 5.30 to 6.74, respectively. Conclusions: Comparison of the LC50 values of isolate 8(2) with those of the reference strain B. t. israelensis showed that this isolate has a higher toxicity potential. Significance and Impact of the Study: Some local Jordanian B. thuringiensis isolates exhibit toxic potential that could be used to control some important pests, and could replace chemical pesticides.