Purpose Successful surgical repair of flexor tendons in the hand relies on establishing adequate repair strength whilst not compromising the biomechanics of freely gliding tendons. Post-operative rehabilitation involves splint and controlled movement, and is intended to prevent adhesions and establishing normal excursion of tendons during work without compromising the repair. This study aimed to investigate the effectiveness of different splinting positions on flexor tendons during digital flexion. Methodology We compared five different heat moulded splints in five different wrist and metacarpophalangeal joint (MCPJ) positions. All four flexor digitorum profundus tendons were isolated in five human adult upper limbs cadaver models and synchronously and repetitively run through an Instron testing frame which involved controlled flexion of the fingers from their maximum extension bounded by the splint to maximal flexion when the finger(s) reached the palm. Outcomes included the maximum force (N) encountered during testing, work of flexion (milliJoules) and displacement at the maximum force (millimetres). Results Splint the wrist and MCP joints at 45 and 30 degrees flexion respectively produced the lowest mean value for maximum force (22.84N, SD 5.28) and second lowest mean value for work of flexion (250.0 mJ, SD 51.34) with acceptable mean displacement (34.11mm, SD 4.21), potentially offering the most favourable splinting conditions. Wrist and MCP joints flexed at 20 and 70 degrees respectively offered potentially less favourable conditions. Conclusion Careful consideration of splinting in post-operative rehabilitation can optimise tendon repair strength and preserve tendon biomechanics with minimal stress on the repaired tendon.