Zeolites are natural or synthetic crystalline aluminosilicates with ion exchanging properties. Although zeolites have been used as animal feed additive for more than 40 years, there is no report about the effects of zeolites on spermatological traits. The aim of this study was to designate the effects of zeolite on the testicular weight, live body weight and spermatological characteristics in rats. Twenty-four, 8- week-old, Sprague–Dawley male rats were used in the study. Rats were weighed and randomly divided into control and feeding groups at the beginning of the study. Feeding groups were formed by adding zeolite at rates of 2%, 4% and 6% to standard rat food. Subsequently the prepared rations were pelleted in 1 cm diameter and fed to the rats for 8 weeks. At the end of the study live weights of all rats were recorded and all animals were anesthetized with sodium thiopental. Then, the testes, epididymis, seminal vesicles and ventral prostate were removed, cleared from the surrounding tissues and testicular weights were recorded for each animal. Cauda epididymis fluid was aspirated by a pipette and spermatological examinations were made. The mean live weight gain during the study was 49.37±17.18, 44.84±10.25, 39.45±5.98 and 47.09±11.49 g in control (0%), 2%, 4% and 6% zeolite groups, respectively (P>0.05). No statistical difference with regard to testis weight and spermatozoon motility could be determined among the groups (P>0.05). However, when compared with all groups the rates of amorphous head (P<0.001), bent at cephalo-caudal junction (P<0.01), and total morphological defects (P<0.001) of the 6% zeolite group were found to be significantly higher. It was concluded that high rates of zeolite could affect the spermatozoon morphology negatively in male animals and the effects of zeolite on reproduction in farm animals require to be studied.