Introduction: Septic arthritis is a prevalent and severe condition. Timely detection and immediate treatment significantly enhance patient outcomes. Objective: This study aims to assess serum procalcitonin as a diagnostic marker for acute bacterial septic arthritis and compare its diagnostic efficacy with synovial white blood cell (WBC) count, erythrocyte sedimentation rate (ESR), and high-sensitivity C-reactive protein (hs-CRP). Methods: We conducted a prospective cross-sectional study involving 100 patients presenting with acute arthritis. Patients with concurrent infections were excluded from the study. Out of 100 cases, 36 patients were diagnosed as acute bacterial septic arthritis and 64 with acute inflammatory arthritis. Blood samples were obtained for complete blood count, ESR, hs-CRP, procalcitonin, and blood culture. Additionally, synovial fluid was analyzed for cell count, Gram stain, crystal identification, and culture. Results: In a study involving 100 patients, 36 were diagnosed with acute bacterial septic arthritis, primarily caused by Staphylococcus aureus and Streptococcus group B. Another 64 patients had acute inflammatory non-septic arthritis, including conditions like gout and rheumatoid arthritis. Serum procalcitonin (PCT)≥0.5 ng/mL showed 59.3% sensitivity, 86% specificity, and a 75.3% positive predictive value for diagnosing septic arthritis. C-reactive protein (CRP) > 10 mg/dL had 78.2% sensitivity, but only 19% specificity. Erythrocyte sedimentation rate (ESR) ≥ 20 mm/h exhibited 95% sensitivity and 19% specificity. White blood cell count (WBC) > 15 × 10^9/L showed 39.1% sensitivity and 66.6% specificity. Conclusion: Serum procalcitonin shows promise in diagnosing acute bacterial septic arthritis, especially when arthrocentesis is not feasible.