Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is a rare clinical-radiological entity predominantly reported in pediatric populations, with limited cases in adults. We present a case of a 27-year-old female who developed transient neurological deficits following influenza A infection. She presented with severe headache, neck stiffness, and limb weakness with sensory deficits. Initial suspicion of meningoencephalitis prompted treatment with intravenous antibiotics and antivirals. However, an MRI revealed a hyperintense splenial lesion in the corpus callosum (SCC), supporting a diagnosis of MERS. The patient achieved full recovery without corticosteroids, reinforcing the self-limiting nature of this condition. This case highlights the diagnostic challenges, imaging findings, and management considerations of MERS, underscoring the importance of clinical awareness to avoid unnecessary interventions in adult cases.