Background: Flexible flatfoot may affect motor control in chronic mechanical low back pain (CMLBP) patients. Objective: This study aimed to assess the motor control in CMLBP with flexible flatfoot. Subject and Methods: This observational study with a cross-sectional and comparative design that was conducted on 52 CMLBP patients assigned into 2 equal groups: Group A (study group) involved 26 CMLBP patients with flexible flatfoot and group B (control group) involved age-matched 26 CMLBP patients with normal foot posture.They aged from 20 to 35 years, and their body mass index ranged from 20 to 25 Kg/m². The motor control was measured using static and dynamic core muscle endurance tests. Results: When comparing CMLBP patients with flexible flatfoot to those with normal foot posture, the results revealed a significant difference in static endurance of the flexor, extensor, and lateral muscles and dynamic core muscles endurance among both groups (P=0.001). Conclusion: When CMLBP patients with flexible flatfoot and those with normal foot posture were assessed for motor control, there were notable differences between the two groups.