This paper describes the use of motion sensors with nine axes to estimate lower limb joint angles during walking and running. Human movement is produced by the rotational motion of the respective joints. Therefore, in an earlier study, the authors estimated knee joint angles by consideration of the centrifugal acceleration and tangential acceleration generated at the thigh and lower leg using motion sensors. For this study, sensor fusion considering centrifugal acceleration and tangential acceleration was applied to estimate the hip, knee, and ankle joint angles in the sagittal plane during walking and running as a first step toward gait analysis using motion sensors. Hip joint flexion and extension were estimated considering the centrifugal acceleration and tangential acceleration caused by three-dimensional rotation of the lumbar. Plantar flexion and dorsiflexion of the ankle joint were estimated considering the centrifugal acceleration and tangential acceleration caused by three-dimensional rotation of the foot. Finally, we evaluated the proposed sensor fusion accuracy for estimation of the lower limb joint angles by comparing the motion sensor results and optical motion capture system results.