Background: Infertility is an ever-increasing problem in today’s world. It can be due to male or female causes. Azoospermia seen in 5–10% of infertile men is due to obstructive or non-obstructive causes. Traditionally, testicular biopsy is the gold standard for evaluation. Fine-needle aspiration (FNA), however, is minimally invasive, provides qualitative and quantitative information about spermatogenesis, and can aid in assisted reproductive techniques making it a novel technique for the evaluation of male infertility. Objective: We aimed to classify different causes of azoospermia into different patterns based upon FNA, and assess the utility of cell indices in classifying cases into different patterns. Method: We conducted a prospective and a retrospective study of 42 azoospermic males, confirmed on semen analysis, over a period of 5 years. Patients were subjected to FNA of the testes. Smears were prepared, air-dried, wet-fixed, and then stained with May-Grünwald Giemsa and Papanicolaou stains, respectively. Cells were identified using predetermined morphologic criteria, and various indices were calculated followed by statistical analysis of the observations. Results: The mean age of 40 patients who satisfied the adequacy criteria was 32.75 years (range 22–48 years). Thirty-four patients had primary infertility and 6 had secondary infertility. Of these, 12 had normal spermatogenesis, 8 had hypo-spermatogenesis, 3 had early and 7 had late maturation arrest, 6 had Sertoli cell-only syndrome (SCOS), and there were different results in each testicle in 4 cases. The Sperm Index (SI) was significantly higher in all cases of normal spermatogenesis than in any of the hypo-spermatogenesis cases (p = 0.009). The Sertoli Index (SEI) in cases of hypo-spermatogenesis and maturation arrest was significantly higher than in cases of normal spermatogenesis (p < 0.001). The Sperm-Sertoli Index (SSI) also showed significant differences between cases of hypo-spermatogenesis and normal spermatogenesis (p < 0.001). These indices were useful in categorising patients with azoospermia. Conclusion: FNA helps to easily and accurately identify all types of testicular cells without biopsy. SI, SEI, and SSI are powerful cell indices for assessing the extent of spermatogenesis and classifying various causes of azoospermia. Bilateral sampling and multiple aspirations give a better mapping of spermatogenesis within the testes. Testicular FNA can thus play a very important role in the evaluation of male infertility.