A study was conducted at the Animal Biotechnology Center of the Institute of Animal Sciences for Southern Vietnam from January 2020 to December 2020. The purpose is to assess the effects of fermenting cashew fruit in diets on the weight gain of sheep. Sixty male sheeps at three months of age (12.72 kg) were designed in a completely randomized with 5 treatments and 3 replications, the treatments were five mixtures of fermenting cashew fruit: Mixture1: 100% cashew fruit + 2% probiotics; Mixture 2: 65% cashew fruit + 30% rice bran + 2% probiotics; Mixture 3: 75% cashew fruit + 25% rice straw + 2% probiotics; Mixture 4: 75% cashew fruit + 25% dried corn plant + 2% probiotics; Mixture 5: 75% cashew fruit + 25% dried cassava waste +2% probiotics. The results showed that the daily weight gain (g) of sheep was 91.37; 89.41, 90.20, and 90.00 for mixture 2, 3, 4, and 5, which were higher the mixture 1. While dry matter and crude protein intake of the Mixture 1 tend to be higher than other treatments.