Background and Purpose: Shoulder pain is a common complication after stroke that can impede participation in rehabilitation and has been associated with poorer outcomes. Evidence-based treatments for hemiplegic shoulder pain are limited. Suprascapular nerve block (SSNB) is a safe and effective treatment of shoulder pain associated with arthritic shoulder conditions, but its usefulness in a stroke population is unclear. Methods: We undertook a randomized controlled trial assessing the effectiveness of SSNB in a population of 64 stroke patients (onset < 1 year) with hemiplegic shoulder pain. The primary outcome was pain measured on a visual analogue scale (VAS). Secondary outcomes were disability (Modified Rankin Scale, Croft Disability Index) and quality of life (EuroQol Health Questionnaire). All participants were assessed before randomization, and at 1, 4, and 12 weeks postintervention. Both groups continued with routine therapy. Results: Although both intervention and control groups demonstrated reduction in pain score, participants who received SSNB consistently demonstrated superior, statistically significant pain reduction compared with placebo. Mean VAS reduction in the SSNB group was >18 mm greater than participants receiving placebo injection. The number needed to treat with SSNB to reduce 1 stroke survivor's pain by 50% at 4 weeks is 4. No significant differences in function or quality of life were observed. No adverse events were reported. Conclusions: Suprascapular nerve block is a safe and effective treatment for patients with hemiplegic shoulder pain.