The present study investigates the effects of dietary commercial Bacilli probiotic (Bacillus subtilis and Bacillus licheniformis) on the growth performance, feed efficiency, body composition and immune parameters of Litopenaeus vannamei. The L. vannamei postlarvae were supplied and acclimated (in 500‐L tanks) to laboratory conditions for 14 days. The shrimps were fed with diets containing 1 × 104 and 1 × 108 CFU/g probiotic Bacilli for 60 days. At the end of the feeding trial, growth performance parameters, body composition, serum biochemical parameters and the hemocytes count were evaluated. Shrimps fed diets supplemented with 1 × 104 and 1 × 108 CFU/g probiotic Bacilli showed improved weight gain, total length, specific growth rate, FCR and survival compared with the control group. The body composition studies revealed higher dry matter, crude protein and ash in shrimps fed with 1 × 104 and 1 × 108 CFU/g probiotic Bacilli. Also, dietary administration of 1 × 104 and 1 × 108 CFU/g probiotic Bacilli decreased serum glucose and cortisol levels. However, significantly increased total protein, lysozyme and hemocyte cell count were noticed in shrimps fed 1 × 104 and 1 × 108 CFU/g probiotic Bacilli. In general, the findings of this study proved that oral administration of 1 × 104 and 1 × 108 CFU/g commercial probiotic Bacilli improved growth performance, feed utilization and immune parameters in whiteleg shrimp (Litopenaeus vannamei).