Advanced imaging techniques, improved operative techniques, and instrumentation combined with better patient awareness and expectations have resulted in an exponential increase in upper limb surgical procedures during recent times. Surgical teams expect superior analgesia and regional blocks have matched these expectations quite often resulting in improved patient satisfaction and early rehabilitation to achieve best results. Ultrasound-guided interscalene brachial plexus block (ISB) is commonly used to provide analgesia for procedures involving shoulder girdle. We report a case of symptomatic hemi-diaphragmatic paresis (HDP) due to the phrenic nerve block following ISB for arthroscopic sub-acromial decompression of the shoulder presenting as severe postoperative dyspnea. There is strong evidence of HDP following ISB in anesthetic literature, but not reported in related surgical specialties such as orthopedics. We wish to inform upper-limb surgeons and educate junior doctors and other ancillary staff working in upper-limb units to be aware of this serious but reversible complication.