Acute abducens nerve palsy; viral-like inflammatory reaction to the vaccine, immune-mediated indirect insult along the abducen nerve; fever; This is a literature report. A previously healthy 59-year-old woman presented emergently to the Eye Institute with acute binocular and painless, horizontal diplopia 2 days after receiving the Pfizer-BioNTech COVID 19 vaccine. She reported 1 day of fever; however, the remainder of her review of systems was unremarkable, and there were no other neurologic symptoms, including facial or generalized weakness, gait abnormality, paresthesias, and anosmia. At presentation, her best-corrected visual acuity was 20 25 in each eye. Intraocular pressure in each eye was within normal limits, and there was no afferent pupillary defect. On sensorimotor examination, the patient had a new right esotropia of 25D in primary gaze, 30D in right gaze, and 10D in left gaze as well as a severe abduction deficit of the right eye. Pictures taken before these ocular motor findings developed demonstrated no prior eye misalignment. Slit-lamp and fundus examination were unremarkable. The erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were both mildly elevated, at 42 mm/hr and 0.8 mg/dL, respectively. Magnetic resonance imaging (MRI) of the brain and orbits with and without gadolinium at time of presentation showed no abnormal signal, enhancement, mass lesion or mass effect. The patient was diagnosed with an abducens nerve palsy with a likely association to the COVID-19 vaccine, given the temporal relationship. Although her fever resolved, her sensorimotor examination remained unchanged at the most recent follow-up. Discussion Abducens nerve palsy is the most frequent isolated ocular motor nerve palsy, with an annual incidence of 11.3/ 100,000. In children, abducens nerve palsies are often associated with trauma, elevated intracranial pressure, neoplasm, or viral infections. This patient developed an acute right abducens nerve palsy following a febrile illness 2 days after receiving the Pfizer-BioNTech mRNA COVID-19 vaccine. Her lack of vascular risk factors, negative review of systems, normal optic nerves, and unremarkable MRI make microvascular or neoplastic etiologies unlikely. Given the patient's mild elevation in ESR and CRP, the Authors hypothesize that this patient developed a viral-like inflammatory reaction to the vaccine, inciting an immune-mediated indirect insult along the abducens nerve. Although less likely in this patient, given the normal MRI, it is also important to consider vaccine related thrombotic events as a possible etiology. The differential diagnosis incudes Duane syndrome, orbit fibrosis, myasthenia gravis, and even temporal arteritis, but all of these are unlikely, given the preexisting photographic evidence, lab findings, scan, and clinical course. These finding has been reported to the CDC and FDA via the Vaccine Adverse Event Reporting System as well as to the manufacturer (Pfizer).; Sender's Comments: The reported abducens nerve palsy was possibly related to the vaccination with Pfizer-BioNTech COVID 19 vaccine due to temporal relationship and no other etiology was found in this case.  The Authors of this article hypothesize that this patient developed a viral-like inflammatory reaction to the vaccine, inciting an immune-mediated indirect insult along the abducens nerve.  The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to Regulatory Authorities, Ethics Committees and Investigators, as appropriate.