Introduction: Acute febrile encephalopathy (AFE) is a significant cause of hospital admissions, often associated with high mortality if untreated. This study aims to assess the cytological and biochemical changes in cerebrospinal fluid (CSF) in febrile patients with altered sensorium, helping in early diagnosis and effective management. Methodology: A prospective study was conducted at PESIMSR, Kuppam, Andhra Pradesh, including 50 patients with fever and altered sensorium. CSF samples were collected via lumbar puncture and analyzed for cytological and biochemical changes. Parameters like CSF glucose, protein, ADA, cell count, and microbial analysis were correlated with patient outcomes. Results: Among the 50 patients, 64% were male, and 36% were female. Most were presented between the 5th and 7th day of fever. The CSF analysis revealed higher cell counts in tuberculosis and bacterial infections than in viral cases. Elevated protein and ADA levels were noted in tuberculosis cases. 88% of patients recovered, while 12% succumbed to the illness. Conclusion: CSF cytological and biochemical analysis is crucial for diagnosing febrile encephalopathy. Elevated cell counts, protein, and ADA levels are significant markers of bacterial and tuberculous infections. Early diagnosis and treatment can improve outcomes.