Phenotypic plasticity and local adaptation are two strategies with which plants acclimate to heterogeneous habitats, facilitating alien species invasions. Eupatorium adenophorum Sprengel is one of the worst invasive species in China. To explore the roles of phenotypic plasticity and local adaptation in E. adenophorum invasion, seedling height, canopy width, branch number and high semi-lethal temperature (HSLT) were measured for six E. adenophorum populations of different altitude origins (640-2450 m) at two common gardens located at high (1400 m) and low (2450 m) altitude, respectively. Seedling height, canopy width, branch number and HSLT (except population of 2130 m origin) were significantly lower at the high altitude garden than at the low altitude garden. The plasticity indices of seedling height (0930-0.956), canopy width (0.881-0.952) and branch number (0.962-0.975) were relatively high, while the plasticity index of HSLT was low (0.052-0.200). At both gardens, the differences among E. adenophorum populations of different origins in seedling height, canopy width and branch number were not significant (P > 0.05), while the difference in HSLT was extremely significant (P < 0.01), showing genetic differentiation. However, the difference in HSLT among the studied populations was still smaller than that between gardens. At high altitude garden, branch numbers of different E. adenophorum populations were positively correlated with altitudes of origins. At low altitude garden, HSLT was negatively correlated with altitude of origin. The above correlations indicate local adaptation of the two variables. Our results indicate that phenotypic plasticity might be more important in E. adenophorum invasion in different altitude habitats than local adaptation, while both of them contribute to E. adenophorum invasion.