Climate warming and anthropogenic activities have led to an increase in the prevalence of non-native plants in mountainous regions that previously exhibited limited occurrences. This phenomenon has resulted in detrimental effects on endemic plants and ecosystem functions. Yet, how traits of non-native plants that successfully spread to high elevation vary along the elevation gradient, as well as the underlying drivers of these changes, remain sparsely understood. In this study, we use Erigeron annuus, a cosmopolitan non-native plant that has invaded to high elevation, as our model to explore its individual biomass pattern along a 1900 m elevation gradient. We also contrast this pattern with the native Artemisia lavandulifolia, which has the same distribution range as E. annuus. We found that the biomass of E. annuus displayed a hump-shape pattern along elevation, while the biomass of native A. lavandulifolia gradually decreased with elevation. By evaluating the effect of climate variables, soil properties, rhizosphere fungal communities and its spatial mid-domain effect (i.e. geographic limitation) on plant biomass, we found that the biomass of E. annuus was primarily influenced by the spatial mid-domain effect, while the biomass of A. lavandulifolia resulted from a complex interplay of climatic variables and rhizosphere microbial communities. Our findings emphasize the importance of a spatial mid-domain effect on the growth of non-native E. annuus along elevation, indicating the impact of E. annuus probable be greatest at mid-elevations and thus, where management priority should be set. Further investigations considering more non-native plant species and species’ traits will allow to scrutinize this vision.