<p><i>Ageratina adenophora</i> is an invasive alien species, that spreads worldwide along subtropical and temperate regions. It has significant negative impacts on natural ecosystems and native flora. However, one of the procumbent native herb <i>Geranium nepalense</i> has been observed frequently with <i>A. adenophora</i>, and their trait variation could be of great significance to understand how they cope with invasion stress. This study aims to analyse trait variation in <i>G. nepalense</i> under <i>A. adenophora</i> canopy. Individual plants of <i>G. nepalense</i> were sampled from highly invaded, moderately invaded and uninvaded sites. The sampled individuals were assessed for ramet densities, lengths of vegetative parts, numbers of flowers and seeds, and their biomasses. The results showed a significant decrease in ramet density but increase in length of vegetative and reproductive parts under both level of invasion. Additionally, numbers of inflorescences were high in both invasion levels compared with uninvaded site; but interestingly, numbers of flowers remained constant. Further, stems and leaves accumulated high biomass under invasion with loss of biomass in seeds. These results conclude that <i>G. nepalense</i> tends to be longer with enlarged vegetative and floral parts under invasion and shifted from procumbent to erect herb. Overall, <i>G. nepalense</i> exhibits adaptive plasticity by strategically reallocating resources and shifting habit under invasion stress. However, decreased seed biomass may have potential negative effects on germination success and early development of progeny. Hence, long-term monitoring is necessary to understand how such responses will influence native plants performance, reproductive success, and persistence of responses to bring some sort of evolutionary changes.</p>