Moringa oleifera Lam, commonly known as moringa, is a plant widely used both as a human food and for medicinal purposes around the world. This research aimed to evaluate the efficacy of the aqueous extract of Moringa oleifera leaves (MoAE) and benzyl isothiocyanate (BIT) in rats with induced breast cancer. Cancer was induced with 7,12-dimethylbenz[a]anthracene (DMBA) at a dose of 60 mg/kg by orogastric gavage once only. Forty-eight rats were randomly assigned to eight groups, each consisting of six individuals. The control group (healthy) was called Group I. Group II received DMBA plus saline. In addition to DMBA, Groups III, IV, and V received MoAE at 100, 250, and 500 mg/kg/day, respectively, while Groups VI, VII, and VIII received BIT at 5, 10, and 20 mg/kg/day, respectively. Treatment was carried out for 13 weeks. Secondary metabolite analysis results identified predominantly quercetin, caffeoylquinic acid, neochlorogenic acid, vitexin, and kaempferol, as well as tropone, betaine, loliolide, and vitexin. The administration of MoAE at a dose of 500 mg/kg and BIT at 20 mg/kg exhibited a notable decrease in both the total tumor count and the cumulative tumor weight, along with a delay in their onset. Furthermore, they improved the histological grade. A significant decrease in serum levels of VEGF and IL-1β levels was observed (p < 0.001) with a better effect demonstrated with MoAE at 500 mg/kg and BIT at 20 mg/kg. In conclusion, this study suggests that both the aqueous extract of Moringa oleifera leaves and the benzyl isothiocyanate possess antitumor properties against mammary carcinogenesis, and this effect could be due, at least in part, to the flavonoids and isothiocyanates present in the extract.