Patients with muscle atrophy undergo rehabilitation exercises by applying resistive force and obstructing foot movement to strengthen their muscles and engage with their neuromuscular system. This can be successfully accomplished without the intervention of a physiotherapist through the use of passive wearable ankle-foot exoskeleton. The existing devices in the market cannot offer bidirectional and variable resistance rehabilitation. This paper proposes the design and development of a passive ankle rehabilitation exoskeleton for bidirectional resistance training with variable stiffness element for ankle torque variation. The conceptual design of the exoskeleton with a variable stiffness element made of Grade 5 Titanium alloy (Ti6Al4V) has been presented along with its kinematic and static analysis. The fabricated prototype of the device was validated using surface electromyogram (sEMG), and the observation clearly depicted improvement in the signal energy during plantar flexion and dorsiflexion. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.