Guillain-Barre syndrome (GBS) is an immune-mediated, often post-infectious illness manifesting as an acute, characteristically monophasic, polyradiculoneuropathy. We present a case of GBS with autonomic involvement following an mRNA-based vaccine against SARS-COV2 (Pfizer/BioNTech mRNA-BNT162b2). A 58-year-old woman presented with fatigue, distal extremity paresthesias, and severe back pain within 3 days after receiving her first vaccine dose. She developed worsening back pain and paresthesias in distal extremities which prompted her initial presentation to the hospital. By the third week post-vaccine, she developed increasing gait unsteadiness, progression of paresthesias, and new autonomic symptoms including presyncopal episodes and constipation. Neurological exam showed bilateral distal predominant lower extremity weakness, decreased sensation in a length-dependent pattern, and areflexia. EMG/NCS showed a diffuse sensorimotor polyneuropathy with mixed demyelinating and axonal features consistent with GBS. She was treated with 2 g/kg of IVIG over 3 days and also received prednisone 60 mg daily for 3 days for severe back pain, with improvement of symptoms. This possible association with mRNA-based vaccination expands the potential triggers for an autoimmune-based attack on the peripheral nervous system.