The objective of this study was to evaluate the efficacy of fungal treatment (Pleurotus ostreatus) of urea-treated rice stubble on growth performance in slow-growing goats. Eighteen crossbred Thai native x Anglo-Nubian male goats (average body weight: 20.4 ± 2.0 kg) were randomly assigned to three experimental total mixed rations containing 35% rice stubble (RS) that was either untreated (URS), urea treated (UTRS) or treated with urea and fungi (UFTRS). URS and UTRS were cultivated and harvested from aseptically fungal spawn, incubated at 25-30 °C for 25 days. Indicators of growth performance were monitored and faeces were collected quantitatively to assess nutrient digestibility, during a 12-week feeding trial. All goats remained healthy throughout experiment. The goats fed UFTRS had a lower feed conversion ratio (kg feed/kg growth) compared to goats fed URS or UTRS. Compared to URS, dietary UFTRS increased nutrient digestibility of slow-growing goats, such as OM (+8.5%), CP (+5.5%), NDF (+39.2%), and ADF (+27.4%). Likewise, dietary UFTRS tended to increase rumen ammonia concentrations but rumen pH and volatile fatty acids were not affected by UFTRS. In conclusion, the present study indicates that the fungal treatment of RS is an effective tool to improve the growth performance of slow-growing goats.