This study evaluates the reliability of isokinetic testing of the knee flexors and extensors in children with cerebral palsy (CP). Twelve children (seven girls, five boys), aged 9 to 15 years, participated in this study. The children's strength was measured bilaterally, using a dynamometer. Each participant was tested twice at an interval of 1 week. During each session, the participant performed five consecutive cycles of knee extension and flexion. Testing velocity was set at 90°/s, and the range of motion was 80°, starting with the knee flexed at 80° and ending in full extension. The measured variable was the peak torque. Reliabilities were determined using intraclass coefficient (ICC) with two-way ANOVA model. The ICCs for individual sessions range from 0.90 to 0.99. ICCs for the eight repetitions over the two sessions range from 0.95 to 0.98. The findings indicate that measuring isokinetic strength in the tested population is highly reliable and should be considered in rehabilitation protocols.