Mikania micrantha, commonly known as Japani Lota in Assam, is an invasive weed native to South and Central America. Despite its reputation as a harmful plant due to its rapid growth and detrimental effects on local ecosystems, it possesses numerous phytochemicals with potential medicinal properties. This study investigates the phytochemical composition of M. micrantha leaves, focusing on their antioxidant, bioregulatory, and chemomicroscopic properties. The leaves were collected from the Golaghat district in Assam, and extracts were prepared using various solvents, including petroleum ether, chloroform, methanol, and water. Phytochemical screening revealed the presence of alkaloids, flavonoids, saponins, terpenoids, and steroids, with methanolic extracts showing the highest diversity of compounds. Additionally, the bioregulatory effect of aqueous leaf extracts was tested on the germination of Cicer arietinum (chickpea) seeds, revealing significant inhibitory effects at higher concentrations. Chemomicroscopic analysis of the stem further identified carboxylated polysaccharides, tannins, and lipids. These findings suggest that M. micrantha possesses bioactive compounds that could be harnessed for therapeutic applications, despite its invasive nature. The study highlights the need for further research into the plant’s potential health benefits and its allelopathic effects on other species, which could contribute to developing novel treatments for various ailments, including diabetes, cancer, and cardiovascular diseases.