We have previously reported the effect of wheelchair with a unique backrest shape with pelvic and thoracic support (P-WC) on healthy individuals. However, the actual effect of P-WC on real users is still unclear. Therefore, the purpose of this study was to investigate the effect of different backrest shapes on asymmetric seated posture and pressure points in patients with hemiplegia. We compared a typical wheelchair with a flat backrest (T-WC) to P-WC. Ten subjects with hemiparesis were analyzed. Outcome measures were body alignment angles and pressure distributions of the supporting surfaces. The total seat pressure decreased (p<0.01) and total back pressure increased (p<0.05), in P-WC compared with T-WC. The head-neck was more upright (p<0.05) in P-WC than in T-WC. Moreover, the center of pressure was located in the middle of both the seat and backrest (p<0.05), and the high unilateral pressure around the ischial tuberosity was dispersed (p<0.05) in P-WC. In conclusion, the backrest shape of the P-WC contributes to reducing postural asymmetry. These results highlight the importance of the shape of the wheelchair backrest for patients with hemiparesis.