Invasive alien species (IAS) introduced through the ornamental plant trade pose significant ecological threats globally, yet public awareness remains poorly studied in the Global South. Since awareness of IAS supports management efforts and encourages behavioral change, understanding knowledge gaps among key stakeholders is essential. Using the Knowledge-Attitudes-Practices (KAP) framework, this study evaluates IAS awareness among ornamental plant buyers and sellers in Bengaluru, India; one of the largest and fastest-growing metropolises in the Global South. Through structured interviews across 44 nurseries, we assessed IAS knowledge, factors influencing awareness, purchasing behaviors, and disposal practices that may contribute to IAS proliferation. Our findings reveal critically low awareness: fewer than 30% of buyers and only 5% of sellers were familiar with IAS concepts, and over 75% of respondents lacked knowledge of plant origins. Invasive species were significantly less recognised than native or non-invasive alien counterparts. However, when informed about the impacts of IAS, 89% of buyers expressed willingness to choose safer plant alternatives, and 57% of sellers indicated they would communicate risks to customers. These results highlight substantial knowledge gaps among urban horticultural stakeholders and underscore the transformative potential of targeted education. Bridging these gaps is critical for integrating IAS management into urban planning and biodiversity conservation across rapidly growing cities in the Global South.