Titanium dioxide, also known as titanium IV oxide or titania found in nature and most widely used in paints, coatings, plastics, foods, cosmetics, skin care products and medicine. In this study, male adult zebrafish individuals were exposed to different doses (1 mg/L, 2 mg/L, 4 mg/L) of titanium dioxide nanoparticles. Acute and sub chronic exposure effects of titanium dioxide nanoparticles on testis tissues were evaluated with histological methods. In addition, roles of titanium dioxide nanoparticle exposure of apoptosis were revealed with TUNEL method. Titanium dioxide exposure inhibits spermatogenesis and cause cell death of spermatogenic cells first time proved with this study. Depending on dose amounts, while an increase in the number of sperm cells, spermatogonia and spermatocytes began to disappear were detected.