The use of Carica papaya leaves in folklore medicine for its antimalarial and antidiabetic activities without reference to its adverse effect is on the increase globally. This study therefore sought to investigate the antifertility effect of C. papaya leaves in male Wistar rats. Fresh and healthy leaves of C. papaya disease were harvested from the Institute of Agricultural Research and Training, Moor Plantation, Ibadan. They were dried and extracted using soxhlet apparatus and ethanol as the solvent. Toxicity test was carried out using standard method. Thirty male Wistar rats were grouped into six of five rats each. Animals in groups A, B and C were administered normal saline for 10, 20 and 30 days respectively via oral route. Those in groups D, E and F were similarly treated but with 500 mg/kg body weight of leaf extract of C. papaya. At the end of treatment, the animals were sacrificed by cervical dislocation. The internal organs were exposed. Testes and cauda epididymis were removed and kept in sterilized glass. Male fertility parameters were determined using standard methods. Ethanolic leaf extract of C. papaya causes decreased sperm count, sperm motility and seminal pH while sperm mortality and abnormality of spermatozoa increased significantly (p<0.05) after 10, 20 and 30 days treatment respectively. These effects were dependent on the number of days treated. The normal range of sperm count, sperm motility, seminal pH and abnormality of spermatozoa are essential factors for fertility. Any disturbance of such normal range of seminal quality may affect the fertility of animals. Thus, these changes in seminal quality of C. papaya leaf treated-animals showed that C. papaya exhibits antifertility activities but this does not automatically translate to such effect on human. Therefore its effect on the fertility of man can be further confirmed.