We present a case of acute partial transverse myelitis (TM) that developed 6 d following covaccination with a bivalent COVID-19 booster vaccine and quadrivalent influenza vaccine. Although initial imaging of the thoracic spine was nonspecific, repeat magnetic resonance imaging (MRI) showed a T2 hyperintense lesion with contrast enhancement, consistent with TM. The risk of rare but catastrophic neurologic complications following the bivalent COVID-19 booster vaccine and/or covaccination with COVID-19 and influenza vaccines is the subject of ongoing investigation in the medical community.