The red flour beetle (Tribolium castaneum) is a common pest insect known for attacking and infesting stored flour and grain. Bacillus thuringiensis (B.t) is a Gram positive, soil dwelling bacteria commonly used as a biological alternative to a pesticide. The present project was designed for the study of combined insecticidal effect of B. t along with boric acid, insecticide cypermethrin and the plant leaves powder, that is, Azadirachta indica against the T. castaneum to check the mortality rate of these insects and LC50 was calculated. Bacteria were isolated from rich soil, pulse dust, grain dust and its growth was checked on the T3 media by applying the microbial techniques. The results obtained show synergism when applied in combined concentration of B.t, boric acid, cypermethrin and powder of neem leaves in 1 g of diet. The combined concentration of each gave higher mortality to larvae and the percentage mortality was calculated as 33, 16 and 16% after 24 h, 41, 25 and 16% after 48 h and 50, 25 and 16% after 72 h in three different combined concentrations as compared to individual concentration. Likewise, in case of adults the percentage mortality was 33, 16 and 13% after 24 h,