Objectives. Identification of cellulolytic microorganisms is of great interest to the hydrolysis of cellulosic biomass. This study focuses on the identification of cellulolytic yeasts and the optimization of cellulase activities produced by the best performing isolate. Results. 30 cellulolytic yeast isolates were selected. Enzymes produced by an isolate from the Trichosporon genus showed the property to hydrolyze different substrates: carboxymethyl cellulose (CMC), cellulose fiber, and filter paper (FP). The optimum measured temperature was 55°C for CMCase and 60°C for FPase. The optimal pH was 5 for CMCase and 4 to 6 for FPase. The effect of the substrates concentration showed that the best activities were obtained at 100 mg/mL CMC or FP. The highest activities were 0.52 for the CMCase and 0.56 for the cellulase fiber at 10 min incubation, 0.44 IU/mL at 15 min incubation, and 24 h FPase preincubation. Conclusion. Cellulases produced by the studied yeast are capable of hydrolyzing soluble and insoluble substrates at elevated temperatures and at a wide pH range. They are considerable interest in the production of fermentable sugars from lignocellulosic substrates.