Adaptive shortening of the pectoralis minor is one of the biomechanical mechanisms associated with subacromial pain syndrome (SPS).To compare the effects of an exercise program alone with an exercise program in combination with pectoralis minor stretching in participants with SPS.Randomized controlled trial.Eighty adult participants with SPS were randomly allocated to two groups. The control group (n = 40) received a 12-week specific exercise program and the intervention group (n = 40) received the same program plus stretching exercises of the pectoralis minor muscle. The primary outcome measure was shoulder function assessed by a Constant-Murley questionnaire, and the secondary outcomes were the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, visual analog scale (VAS), and pectoralis minor resting length.The present study shows no difference between the two interventions according to the Constant-Murley questionnaire (1.5 points; p = 0.58), VAS at rest (0.2 cm; p = 0.11), VAS at movement (0.5 cm; p = 0.08), and pectoralis minor resting length (0.3 cm; p = 0.06). The DASH questionnaire showed greater functional improvement in the control group (5.4 points; p = 0.02). Finally, only pectoralis minor length index showed difference statistical significant in favor of intervention group (0.3%; p = 0.04).In the short-term, the addition of a program of stretching exercises of the pectoralis minor does not provide significant clinical benefit with respect to functional improvement or pain reduction in participants with SPS.Brazilian registry of clinical trials UTN number U1111-1210-3555. Registered 5 March 2018.