Urtica dioica L. has been used traditionally for centuries. U. dioica leaves and roots are used as a blood purifier, emmenagogue, and diuretic, as well as to treat menstrual hemorrhage, rheumatism, and eczema. The present study aimed to evaluate the activity of U. dioica L. aerial parts in endometriosis rat model.To evaluate the effects of the plant in endometriosis, n-hexane, ethyl acetate (EtOAc), and methanol (MeOH) extracts were prepared from the aerial parts of the plant and utilized in a rat surgical endometriosis model. In this model, adhesion scores of endometriotic implants and the spherical volumes of ectopic uterine tissues were evaluated. In addition to these parameters, tumor necrosis factor alpha (TNF-α), vascular endothelial growth factor (VEGF), and interleukin-6 (IL-6) levels of the peritoneal fluids were evaluated. Furthermore, histopathological studies were conducted on the endometriotic tissues.Post-treatment implant volumes and adhesion scores were significantly reduced in the reference and the MeOH extract treated groups. Significant differences were found between the peritoneal TNF-α, VEGF, and IL-6 levels of MeOH extract treated group and those of control group. Moreover, histopathological findings supported the biological activity results. Furthermore, isolation studies were conducted on the MeOH extract, which showed prominent activity in the rat endometriosis model. Rutin (1), isoquercetin (2), the mixture of kaempferol-3-O-rutinoside (nicotiflorin) (3a) and isorhamnetin-3-O-rutinoside (narcissin) (3b) (3), the mixture of kaempferol-3-O-glucoside (astragalin) (4a) and isorhamnetin-3-O-glucoside (4b) (4) were isolated from the active fraction.The present study demonstrated that aerial parts of U. dioica exhibited promising activity in the endometriosis rat model due to its flavonoids.