Anterior seat inclination has been applied in children with spastic diplegic cerebral palsy (SDCP) to adjust alignment during sitting. However, there has been a lack of evidence reporting the effects of anterior seat inclination on sit-to-stand (STS) performance in children with SDCP. Therefore, the aim of the study was to investigate the effects of anterior seat inclination on STS performance in children with SDCP. Fourteen children with SDCP (aged 8.74 (1.79) years, GMFCS levels I and II) participated in this study. All participants performed STS in four conditions of the seat including the horizontal seat (HS), anterior seat inclination of 5° (A5), 10° (A10) and 15° (A15). Three-dimensional motion analysis system was used to capture STS movements. The total movement time and total mechanical work during the STS with A5, A10 and A15 were significantly lower than STS with HS. At the beginning of the task, STS with A5, A10 and A15 showed less trunk and hip flexion than HS. Anterior seat inclination with 5°, 10° and 15° could improve STS performance in children with SDCP. Therefore, applying these seats would be another option for children with SDCP to enhance STS performance.IMPLICATIONS FOR REHABILITATIONAnterior seat inclination could improve sitting posture in children with diplegia.Children with diplegia spent less time when STS from the anterior seat inclination.Children with diplegia used less energy when STS from the anterior seat inclination.