Objective: To investigate the effect of laser photostimulation in rehabilitation of human digital flexor tendons with a placebo-controlled double-blind prospective study model. Background Data: Low-energy laser therapy has been applied in several rheumatoid and soft tissue disorders with a varying rate of success and it has also been shown to have a positive effect on tendon healing in animal experiments, but no clinical study on laser photostimulation in the treatment of human tendons has been reported to date. Materials and Methods: This study was performed in a total of 25 patients with 41 digital flexor tendon injuries in five anatomical zones. In Group I (21 digits in 13 patients), whirlpool and infrared GaAs diode laser with a frequency of 100 Hz. was applied between the 8(th) and 21(st) days postoperatively and all patients were given the Washington rehabilitation program until the end of the 12(th) week. In Group II (20 digits in 12 patients), the same treatment protocol was given but the laser instrument was switched off during applications. Results: The results of the study showed a significant improvement in the laser-treated group only for the parameter of edema reduction (p < 0.01) but the difference between the two groups was non-significant for pain reduction, hand grip strength, and functional evaluation performed according to Strickland and Buck-Gramcko systems using total active motion and fingertip-to distal palmar crease distance parameters (p > 0.05). Conclusions: Significant improvement obtained in edema reduction both immediately and 12 weeks after supplementary GaAs laser application in our study has been interpreted as an important contribution to the rehabilitation of human flexor tendon injuries because edema is known to have a detrimental effect on functional recovery during both early and late stages of tendon healing. However, our study has failed to show a significant positive effect of supplementary GaAs laser application on the other functional recovery parameters of human flexor tendon injury rehabilitation and we suggest further clinical study in this topic be done using different laser types and dosages in order to delineate the role of this promising treatment modality.