Thirty-four males with Achilles tendon ruptures were randomized to receive photobiomodulation during the 8-week cast immobilization (n=17) or sham photobiomodulation (n=17). The primary outcome of interest was the Achilles tendon rupture score (ATRS). Secondary outcomes of interest included pain at rest and during effort on a Numeric Pain Rating Scale (NPRS), ankle range of motion, and plantar flexor muscle strength. Outcomes were assessed at 8, 12 and 16 weeks post-rupture. The results found no difference in function (ATRS scores) with photobiomodulation vs. control. Moreover, no differences in range of motion, pain at rest, or plantar flexor muscle strength were observed between the two groups. Pain during walking was, however, significantly lower in the photobiomodulation group at 12 and 16 weeks follow-up.