The demand for sustainable and eco-friendly control methods of pests and insects is increasing worldwide. From this came the interest in Bacillus thuringiensis, an entomopathogenic bacterium capable of replacing chemical pesticides. However, the possibility of pests developing resistance to a particular strain may impair its use, and there is a need to identify novel strains of this species as potential commercial biopesticides. B. thuringiensis sv. israelensis is one of the most successful serovars, widely commercialized for its activity against black fly and mosquito larvae. In this study, we isolated, characterized, and sequenced a new Lebanese B. thuringiensis sv. israelensis isolate, strain AR23. Compared to the commercialized reference strain AM65-52 (Vectobac (R), Sumitomo), AR23 showed an increased activity against several mosquito species. The genomic analysis revealed that this strain, compared to AM65-52, possesses a simplified plasmid content and an additional functional cry4Ba coding gene that most likely accounts for the increased effectiveness of this strain in mosquito larvae killing.