Rodents cause significant damage to many crops, spread diseases, and pose a severe risk to public health. Several synthetic contraceptive agents are available for controlling rodents; however, their use is associated with toxic effects on non-target organisms. Penicillium oxalicum has several medical properties, but no reports were available on fertility. This study aimed to assess the antifertility potential of n-butanol and ethyl acetate extracts of P. oxalicum in adult male albino rats as biological control agents by lowering the population size of rodent pests. Rats were assigned into three groups (n = 36). The first control group (GI) was injected intraperitoneally with 0.5% dimethyl sulfoxide (DMSO). The second (GII) and third (GIII) groups were injected with a single dose of 200 mg/kg body weight (b.wt.) of n-butanol and ethyl acetate extracts of P. oxalicum intraperitoneally, respectively, after dissolving in 0.5% DMSO. Further, P. oxalicum was identified morphologically and molecularly and then submitted with accession number OM282858 to the National Center for Biotechnology Information (NCBI) GenBank. The antifertility potential of P. oxalicum was evaluated after 24 h (the injection period), 96 h, and 168 h (the recovery periods) of treatments. The effects of the treatments on organ weight, testicular histology, histomorphometry measurements, and sperm characteristics were assessed. Both P. oxalicum extracts caused changes in reproductive organ weights, testicular histology, histomorphometry measurements, and spermatogenic arrest accompanied by a significant decrease in the count of epididymal sperm and its motility and an increase in the percentage of sperm abnormalities during the injection and recovery periods. Thus, the results suggest that both P. oxalicum extract treatments cause suppression of fertility in adult male rats. Therefore, these outcomes are essential for public health, farming establishments, and vertebrate pest control managers.