Endophytes and rhizospheric microorganisms support invasive species’ adaptation to environmental stresses. Here, we review the impacts of endophytes, rhizospheric microbes (particularly symbiotic nitrogen-fixers), mycorrhiza and pathogens on plant invasion in arid and semi-arid areas. Endophytes and soil microorganisms either enhance nutrient acquisition for enhancing the invasive plant immune system and/or negatively affect native plants. In addition, the positive feedback between mycorrhizal fungi and invasive plants enhances the competitive ability of the aliens, providing them more opportunities for success, establishment, and dominance. The microbes and their secondary metabolites promote invasive plant species by changing soil microbial community structure and carbon biomass as well as enzyme activity, which improves soil properties and processes. The negative impact of invasive exotic plants on the associated biota and the role of allelochemicals are also discussed. It could be concluded that endophytes interact with rhizosphere microbes to promote invasive plant species in arid and semi-arid areas in a way similar to what happens in other ecosystems; the differences are in the pathways and reactions, which depend upon the prevailing abiotic factors. More interdisciplinary field experiments integrating microbial, biotechnological, and molecular approaches are needed to understand the role of symbiotic microbes in invasion biology.