While the evidence supports a role for the soil microbiome to modulate the environmental tolerance of various plant species, its role in the invasion success remains seldom assessed. Here we show results from two complementary experiments aimed at understanding the role of the soil microbiome on the performance of T. officinale (dandelion) plants. Since the relative importance of soil microbiome on plant fitness can differ between native versus introduced origins, we conducted a full cross-transplant experiment to compare the plant performance from different origins (native/introduced) in their original or exotic soils, along with manipulated soil microbiome. In addition, since the relevance of soil microbiome for plant fitness can depend on the level of environmental stress, we compared the plant performance under different soil microbiome treatments in an introduced latitudinal gradient. We found positive effects of soil microbiome on performance traits for T. officinale plants from most of the evaluated populations, being particularly relevant for plants in the introduced range and under stressful conditions.