This cross sectional descriptive study was done to observe the mean diameter of seminiferous tubules and to determine its differences between different age groups in Bangladeshi male. Thirty human testes of different age groups were collected by purposive sampling technique. Among them 22 specimens were collected from cadavers during routine postmortem examination and 8 specimens were from dead fetuses from Gynaecology & Obstetrics Department. The specimens were grouped into three categories Group A (28 to 42 weeks of gestational age), Group B (Up to 14 years) and Group C (15 to 70 years). The mean diameter of seminiferous tubules was measured and significant differences of the dimensions between different age groups were determined. The mean±SD diameter was 85.37±15.51 μm in Group A, 144.04±63.34 μm in Group B and 227.92±22.47 μm in Group C. Statistically, differences between age groups were calculated by using Unpaired Students 't' test. The present study revealed that the diameter increased with age and mean differences were statistically significant between Groups A&C, B&C and A&B.