This study was performed to examine the convergent and discriminant validity of the Pediatric Balance Scale (PBS), a modified version of the Berg Balance Scale (BBS), in children with spastic cerebral palsy (CP). A total of 38 children (age, 4 to 10 years) with spastic CP who could ambulate participated in this study. PBS, equilibrium scores of Sensory Organization Test derived from computerized dynamic posturography, Gross Motor Function Measure (GMFM), and Pediatric Evaluation of Disability Inventory (PEDI) mobility skills were evaluated. With regard to convergent validity, PBS total score was moderately correlated with equilibrium score under the condition with eyes open, fixed foot support and condition with eyes closed, fixed foot support (rs = 0.579, eye open; rs = 0.448, eye closed; p < 0.05). PBS total score was highly correlated with GMFM scores (dimensions D and E; total GMFM-88; and GMFM-66) and capability, of the PEDI mobility domain, and moderately correlated with performance of the PEDI mobility domain. Discriminant validity indicated that PBS total score can distinguish between different Gross Motor Function Classification Scale levels in children with CP. PBS can be considered a simple, valid scale for examining functional balance capacity in children with spastic CP. Furthermore, it can better predict motor capacity and capability than equilibrium score and motor performance.