Use of antibiotics as an additive in poultry diets to improve growth has been banned in several country. A popular alternative to the use of antibiotics has been use of probiotics. The study was conducted to investigate the effect of dietary inclusion of cassava yeast as a probiotic source on growth performance and carcass percentage in Japanese quails. Three hundred and twenty Japanese quails (1 day of age), were used. The Japanese quails were randomly allocated to 32 pens containing 10 birds each with 8 replicates and assigned to receive one of four dietary treatments (1.Control, 2. S. cerevisae 1×10⁶organisms/kg, 3. S. cerevisiae 1×10⁷ organisms/kg, 4. S. cerevisiae 1×10⁸ organisms/kg) in a completely randomized design. The results showed that feed intake, feed conversion ratio, average daily gain and carcass percentage were not significantly different among treatments (p>0.05). However, significant differences were observed in feed intake at weeks 5 and average daily gain at week 2. The results of the present experiment showed that dietary inclusion of cassava yeast as a probiotic to Japanese quail seems to have minimal influence on growth performance and carcass percentage. © Asian Network for Scientific Information, 2009.