AbstractXylanase treatment can be an environmentally friendly way to improve the formability and drainability of chemi-mechanical pulp (CMP). Improvements in xylanase treatment efficiency are possible with application of an ultrasonic wave via the cavitation effect. Results showed that the specific surface area (SSA) of the combined treated pulp increased by 14.6% at an ultrasonic treatment of 30 min and xylanase dosage of 10 U/g, in comparison to xylanase treatment alone. Also, the drainability of xylanase-treated pulp increased from 450 to 500 mL, and it further increased to 775 mL with ultrasonic-assisted xylanase treatment. Morphological characterization of pulps showed an enhanced fibrillation for the combined treatment, as shown by scanning electron microscope (SEM) images. In addition, the dimensions of treated fibers were negligibly affected.