Industrial production of Tenebrio molitor larvae (TML), a promising source of protein for food, requires safety, fast growth, maturation, and high survival. Probiotics, enhance host growth and protect against pathogens and diseases. This study evaluates the effects of three probiotic bacteria immobilized on the diet of mealworms, on growth performance, nutritional value, and microbial load of T. molitor larvae. The bacteria employed were Bacillus subtilis, Bacillus toyonensis and Enterococcus faecalis, all presenting probiotic properties. The highest larvae weight and length gain and shorter time to pupation were observed in the E. faecalis series. Following probiotic administration, the crude protein content increased, and crude fat was reduced. The highest protein values were observed in E. faecalis series, the highest dry matter content when B. toyonensis and B. subtilis were employed, and the lowest fat content in B. subtilis series. Fatty acid analysis showed significantly decreased content of palmitic and myristic acid and increased levels of stearic acid in all treatments. Microbial load analysis showed a decrease in Enterobacteriaceae by 46 and 99% in B. subtilis and B. toyonensis series, while coliforms and endospores were significantly reduced in all probiotic series. Addition of probiotic bacteria in T. molitor larvae diet resulted in a significant improvement in terms of growth enhancement, nutritional fortification, and microbial load reduction. In conclusion, probiotic bacteria in TML diet result in the faster production of nutritious and safe insects, to cover insect food market demands.