Hyptis suaveolens is an exotic invasive weed in many areas of West Bengal, India. The allelopathic potential of leaf extracts and leachates of H. suaveolens was investigated on germination and metabolism of mung bean seeds (Vigna radiata cv. K851). The extracts and leachates reduced the germination and seed viability. The insoluble carbohydrates, proteins, and the activities of dehydrogenase and catalase enzymes were significantly reduced. Amino acid and soluble carbohydrate levels were increased in seeds pretreated with leaf extracts and leachates. The overall biochemical results indicate that various inhibitors present in H. suaveolens impart strong inhibitory effect on mung bean. The leaves of H. suaveolens possess phytotoxic chemicals, which potentially rendered the inhibitory action on mung bean seeds and provided key information for the proper management of H. suaveolens and other invasive weeds showing similar behavior.