Introduction: Parsonage–Turner Syndrome (PTS) is a rare disease of the brachial plexus of unclear aetiology. The limited data available typically describes involvement of branches of brachial nerves. The authors present a case of PTS with a rare combination of unilateral brachial plexus, phrenic nerve, and recurrent laryngeal nerve injuries. They also highlight successful treatment with pharmacological intervention despite several months’ delay in diagnosis. The 35-year-old female presented with acute onset of severe left shoulder pain followed by severe progressive weakness of the left shoulder muscles, progressive weakness of her voice, nasal regurgitation of fluids, paroxysmal bouts of coughing, and exertional dyspnoea at rest. The symptoms remained undiagnosed for about 10 months. A clinical diagnosis of exclusion of PTS was finally made, and treatment with steroids, neurotropic drugs, and physiotherapy was started. The patient has recovered significantly since then and continues to improve. Conclusion: The authors presented a case of PTS with a rare combination of brachial plexus, recurrent laryngeal nerve, and phrenic nerve injuries. This case was also remarkable for the significant improvement in her symptoms with treatment, despite the delay in diagnosis. This bears evidence that steroids and adjuvant therapy is useful even months after onset of the disease.