In this work, a 3-D porous hydroxyapatite (HA)-decorated thermoplastic polyurethane (TPU) scaffold with high porosity and excellent biocompatibility was successfully fabricated using a simple ultrasonic method. It was found that HA nanoparticles were successfully introduced onto the surface of the TPU scaffold, and a strong interaction occurred between the HA nanoparticles and the TPU matrix. The porosity was calculated to be about 87%. The water contact angle decreased from 121.1 degrees for TPU to 44.6 degrees for HA-decorated TPU scaffolds. The water absorption and mechanical properties of HA-decorated TPU scaffolds were significantly higher than those of TPU scaffolds. Compared with TPU scaffolds, the addition of HA nanoparticles effectively improved the attachment and growth of mouse embryonic osteoblast cells (MC3T3-E1) cultured on the HA-decorated TPU scaffolds. These results suggest that HA-decorated TPU scaffolds possess great potential to be used as tissue engineering scaffolds. Furthermore, the ultrasonic technique could be used as a simple, effective, and universal method for decorating tissue engineering scaffolds.