Lack of contraceptive choices which meet the requirements is one of the contributing factors to less participation of man in contraceptive use. This research aimed to study the effectiveness of natural material for alternative male contraception, by injecting papaya seed extract with Cibinong variety (Carica papaya L.) to long tail monkey (Macaca fascicularis L). The research was conducted at Primates Study Center, Institute of Agriculture, Bogor. Total samples of this research were 8 monkeys, with three intervention groups and one control group. Papaya seed extract was injected via intramuscular in 21 days, with dose for each group were 40 mg/monkey, 80 mg/monkey, and 120 mg/monkey. Data analysis of spermatozoa quality (motility, viability, morfology) was done by using Cochran test before and after intervention stages, and during recovery stage. Meanwhile, data aalysis of spermatozoa concentration and testosterone hormone level was done by using Friedman test. Result of this reseach demonstrated reduction of motility, viability, and morfology of spermatozoa after inejction of papaya seed extract and increase to normal level at recovery stage (p ≤0.05). These results was supported with cement aglutination. The most effective dose was at 40 mg/monkey/day, with reduction of spermatozoa motility from 87.5 % to 40%, and reduction of testosterone level from 2.35 ng/mL to 1.83 ng/mL. Even though spermatozoa motility and testosterone hormone level reduced, but its conditions were still in good condition category.