Our aim in this study was to examine relationships between the motor activity ability, sensor-based kinematics and forward-backwards gait characteristics of children with cerebral palsy (CP). In this prospective cross-sectional study we studied 40 children with CP. We used the Pediatric Motor Activity Log Revised (PMAL-R) to assess motor activity, evaluated motion kinematics (acceleration and angular velocity) with a sensor-based application, applied the Edinburgh Visual Gait Score (EVGS) and the Timed Up and Go Test (TUG) to observe gait performance, and used the Three Meter Backward Walk Test (3MBWT) to assess backward gait. We found moderately positive significant correlations (r1 = 0.416, r2 = 0.418, p < 0.05) between the chilidren's minimum angular velocity on PMAL-R motor activity frequency (how often) and quality (how well) scores, respectively. We also found moderately negative significant correlations (r1 = −0.529, r2 = −0.521, p < 0.05) between PMAL-R frequency (how often) and quality (how well) scores with TUG, respectively. There were moderately high positive correlations (r1 = 0.415, r2 = 0.726, p < 0.05) between EVGS scores and 3MBWT and TUG scores, respectively. We concluded that angular velocity ability was moderately related to children’s motor activity and showed that physical performance tests (TUG and 3MBWT) could monitor gait function and upper extremity motor activity level, including both forward and backward walking tasks, in children with CP.