This retrospective observational study evaluated the diagnostic and predictive value of serum Inhibin B (INHB), follicle-stimulating hormone (FSH), and the INHB/FSH ratio in differentiating histopathological subtypes of non-obstructive azoospermia (NOA) in men undergoing microdissection testicular sperm extraction (micro-TESE). Seventy-three patients treated at a single tertiary referral center between January 2023 and September 2025 were included. Hormonal parameters were assessed preoperatively, and histopathological findings were categorized into five groups (SCOS, EMA, LMA, HSG, NS). The INHB/FSH ratio demonstrated significant discriminative ability across histopathological patterns and showed strong predictive performance in ROC and regression analyses. These findings suggest that the INHB/FSH ratio may serve as a practical, non-invasive biomarker for estimating testicular pathology severity in NOA patients.