Gait analysis is useful in characterizing impaired gait in patients with various neuromusculoskeletal disorders. Contemporary gait analysis is conducted using numerous motion capture cameras and force plates. However, this setup is restricted to a constrained and artificial testing environment, which may lead patients to make unnatural movements that poorly represent real-world human gait. We proposed a shoe-mounted gait analysis system composed of two 9-axis Inertial Measurement Units (IMUs), an IR sensor, and a pair of instrumented shoes. The system was validated against a state-of-the-art gait lab in a study with ten subjects. The results showed that the system was able to estimate the 3D kinematics, the global Centre of Pressure (COP), and gait parameters such as step length and gait phases acceptably well. This work provides a portable and unobtrusive method of performing lower-limb gait analysis in unconstrained and ambulatory environments.