The Honda Walking Assist® (HWA) is a light and easy wearable robot device for gait training, which assists patients' hip flexion and extension movements to guide hip joint movements during gait. However, the safety and feasibility of gait training with HWA after total knee arthroplasty (TKA) remains unclear. Thus, we aimed to evaluate the safety and feasibility of this gait training intervention using HWA for a patient who underwent TKA. The patient was a 76-year-old female who underwent a left TKA. Gait training using HWA was conducted for 18 sessions in total, from 1 to 5 weeks after TKA. To verify the recovery process after TKA surgery, knee function parameters and walking ability were measured at pre-TKA and 1, 2, 4, and 8 weeks after TKA. The gait patterns at self-selected walking speed (SWS) without HWA at pre- and 5 weeks after TKA were measured by using 3-dimensional (3D) gait analysis. The patient completed a total of 18 gait training interventions with HWA without any adverse complications such as knee pain and skin injury. The postoperative knee extension range of motion (ROM), knee extension torque, SWS, and maximum walking speed were remarkably improved. Regarding gait kinematic parameters, though this patient had a characteristic gait pattern with decreased knee ROM (called stiff knee gait) preoperatively, the knee flexion angle at 5 weeks after TKA showed knee flexion movement at loading response phase (LR; called double knee action), increased knee ROM during gait, and increased knee flexion angle at swing phase. In this case, the gait training using HWA was safe and feasible, and could be effective for the early improvement of gait ability, hip function, and gait pattern after TKA.