Hypermobility syndrome (HMS) is characterised by generalised joint laxity and musculoskeletal complaints. Gait abnormalities have been reported in children with HMS but have not been empirically investigated. The extent of passive knee joint range of motion (ROM) has also not been well reported in children with HMS. This study evaluated gait kinematics and passive knee joint ROM in children diagnosed with HMS and healthy controls. Thirty-seven healthy children (mean age±SD=11.5±2.6 years) and 29 children with HMS (mean age±SD=11.9±1.8 years) participated. Sagittal knee motion and gait speed were evaluated using a VICON 3D motion analysis system. Passive knee ROM was measured with a manual goniometer. Independent t-tests compared the values of sagittal knee motion and gait speed between the two groups. Mann-Whitney U tests compared passive knee ROM between groups. Passive ROM (extension and flexion) was significantly higher (both p<0.001) in children with HMS than the healthy controls. Peak knee flexion (during loading response and swing phase) during walking was significantly lower (both p<0.001) in children with HMS. Knee extension in mid stance during walking was significantly increased (p<0.001) in children with HMS. However, gait speed was not statistically (p=0.496) different between the two groups. Children with HMS had higher passive knee ROM than healthy children and also demonstrated abnormal knee motion during gait. Gait re-education and joint stability exercise programmes may be of value to children with HMS.