<p><i>Erigeron bonariensis</i> L. (syn. <i>Conyza bonariensis</i>), a member of the Asteraceae family, has gained considerable scientific attention because of its medicinal and allelopathic potential. This review provides an overview of botanical characteristics, distribution, and phytochemical composition of <i>E. bonariensis</i>, highlighting its bioactive compounds with therapeutic and allelopathic significance. Rich in secondary metabolites, such as phenolic acids, flavonoids, terpenoids, alkaloids, and sesquiterpene lactones, the plant exhibits potent antioxidant, anti-inflammatory, and antimicrobial activities. Traditionally used to treat a wide range of ailments, it also demonstrates strong allelopathic effects by releasing biochemical compounds that suppress the growth of surrounding plant species. Compounds such as (4Z)-lachnophyllum lactone, which mediates allelopathic potential, offer opportunities for eco-friendly weed management in agriculture. Beyond its herbicidal activity, <i>E. bonariensis</i> has shown potential in managing other agricultural pests, including fungi, nematodes, insects, and bacteria, thereby presenting itself as a multitarget natural pest control agent. These multifunctional properties make it a promising candidate for developing eco-friendly bioherbicides and biopesticides, reducing reliance on synthetic agrochemicals. The use of synthetic pesticides disturbs the ecology of biotic communities, and is hazardous to the environment and human health. However, limited comparative studies with related invasive Asteraceae species and inconsistent phytochemical extraction protocols have hindered their broader application. This review underscores the dual ecological and pharmacological roles of <i>E. bonariensis</i> and advocates its integration into sustainable agriculture and healthcare systems. This further suggests that utilizing invasive species, such as <i>E. bonariensis,</i> for beneficial purposes can turn biological threats into valuable biotechnological assets.</p>