A bacterial formulation containing spores of a Brevibacillus laterosporus strain from Sardinia, known to be toxic by ingestion to the house fly (Musca domestica), was assayed in laboratory, outdoor, and field conditions for the control of immature stages of this pest. In all laboratory assays, the bacterial formulation exhibited toxicity against house fly larvae. A concentration of 1 × 10⁸ spores of B. laterosporus/g of diet caused 100% mortality of house fly immature stages. The same formulation, applied at a concentration of 1 × 10⁸ spores/ml, equivalent to a dose of 2 liters/m², caused a reduction in adult emergence from laboratory and natural breeding substrates (outdoor cage experiments) up to 80.3 and 57.8%, respectively. Similarly, this formulation applied in the cow pen of a diary farm at a dose of 2 liters/m² produced a significant reduction (30%) in immature fly development. Therefore, the use of this bacterial preparation in microbiological control strategies for the integrated pest management of this species is promising.