This study was designed to evaluate the reproductive toxicity of Cassia absus seeds, which have been used in Persian folk medicine. Female rats in treatment groups (N = 5) received C. absus n-hexane fraction (CAF) at oral doses of 100, 200, and 500 mg/kg b.wt./day, once per day on days one to five post-coitum (pc). The control group received 0.2 mL of olive oil (vehicle). Fertility, maternal index, hormone level, and teratogenicity were evaluated. Phytoconstituents of the seeds were detected by HPTLC and GC-MS. The presence of phytoprogesterones was evaluated by docking software. The fertility index and number of fetuses in treated groups decreased significantly. Missed abortion was 50% after administration of 500 mg/kg/day of CAF. The maternal body weight, uterine weight, and levels of FSH, LH, and estradiol exhibited insignificance changes. The serum concentration of progesterone also changed significantly in a dose-dependent manner. No teratogenic effect was found. Oleic acid (35.89%) and linoleic acid (24.22%) were the major constituents of the seed oil. In addition, chaksine and β-sitosterol showed potential phytoprogesteronic properties in docking studies. The reproductive toxicity of C. absus seeds may be related to a hormonal imbalance, a decline in the fertility index, and an increase in the rate of missed abortions of fetuses.