The purpose of this study was to develop and test the validity and reliability of the GaitGrabber System in measuring kinematic variables in the sagittal plane during gait. Eighteen individuals participated in the reliability study and 28 in the concurrent validity study. The Qualisys Pro-Reflex System used as a gold standard reference system. The GaitGrabber calculates the relative angles at the hip, knee and ankle in the sagittal plane. The Intraclass Correlation Coefficient (ICC) was used to compare the average of the angular peaks between visits. The principal component analysis was used to test the validity of the system. The ICC ranged from moderate to excellent and the validity of the system was proved for the ankle. There were significant differences in the range of motion for the hip and knee joints which were attributed to different instrumental characteristics. The GaitGrabber system is valid and reliable and can be clinically used to analyze kinematics during gait in the sagittal plane.