Objective: To investigate the effectiveness of thermal and sub-thermal capacitive resistive 448kHz monopolar radiofrequency (CRMRF) plus exercise compared to Sham CRMRF plus exercise on pain, functionality, and quality of life in patients with subacromial pain. Material and methods: A randomized sham-controlled double blind clinical trial was designed. Eighty-one participants with subacromial pain were enrolled and randomly assigned to three intervention groups (Thermal CRMRF, Sub-thermal CRMRF, and Sham CRMRF). The main outcomes variables were for pain: visual analogic scale (VAS) and pressure pain threshold, for functionality: shoulder pain and disability index (SPADI) and Quick- Disabilities of the Arm, Shoulder and Hand (Quick-DASH) and for quality of life: European Quality of Live Five Dimensions (EQ-5D). Variables were measured at baseline, post-intervention, and at one-month and three months follow-ups. An intention-to-treat analysis was realized. Results: All three groups statistically (p<0.01) and clinically significantly improved pain (VAS) and functionality (SPADI) respect to baseline at post-intervention and follow-up periods. The improvement in Quick-DASH outcome respect to baseline at one month follow-up was clinically relevant only in the thermal CRMRF group (-16.8 points; CI95% -27.3 to -6.3). Thermal-CRMRF group showed a greater effect on Quick-DASH at one month follow-up (-14.1 points, CI95% -28.1 to -0.1) compared with Sham-CRMRF group. EQ-5D measure at one month follow-up only improved in thermal-CRMRF group (0.12 points; CI95% 0.01 to 0.23). Only thermal-CRMRF group improved the pressure pain threshold outcome (0.42 kg/cm2 CI95% 0.05 to 0.79) at post-treatment.