The rhizosphere plays a vital role in the exchange of materials in the soil–plant ecosystem, and rhizosphere microorganisms are crucial for plant growth and development. In this study, we isolated two strains ofPantoearhizosphere bacteria separately from invasiveAlternanthera philoxeroidesand nativeA. sessilis. We conducted a control experiment to test the effects of these bacteria on the growth and competition of the two plant species using sterile seedlings. Our findings showed that the rhizobacteria strain isolated fromA. sessilissignificantly promoted the growth of invasiveA. philoxeroidesin monoculture compared to nativeA. sessilis. Both strains significantly enhanced the growth and competitiveness of invasiveA. philoxeroidesunder competition conditions, regardless of their host source. Our study suggests that rhizosphere bacteria, including those from different host sources, can contribute to the invasion ofA. philoxeroidesby significantly enhancing its competitiveness.