Background: ''Suprascapular nerve block'' is a well known technique for treating chronic shoulder pain. Ultrasonography-guided nerve block is a new technique hoping to decrease the complications of inadvertent injection of drug into the vessels or nerve sheet by increasing the accuracy and efficacy of the injections. Methods: In a trial clinical study, 50 Patients suffering from chronic shoulder pain were divided randomly into two groups. In the first group, nerve block was applied under the ultrasonograpy guide and in the second group using direct anatomic landmarks (Moore technique). Pain score was assessed using a visual analog scale (VAS) and shoulder function was evaluated by constant shoulder score (CSS) before the injection and after the block. The patients' satisfaction rate and efficacy were also evaluated and compared between the two groups. Results: There was no statistically significant difference between the two groups in pain or shoulder functional scores before the procedure (p≥.05). One week after the nerve block, the first group revealed significantly improvement in pain score p=.035). Although shoulder function improved in both groups, the difference was not significant. (p≥.05). One month later, pain and shoulder functional scores showed better improvement in group one compared to group two (p=.000). No complication occurred in either group. Conclusion: Ultrasonography-guided suprascapular nerve block has better outcome in pain score and shoulder function compared with ''blindly'' blocking the nerve.