Arbuscular mycorrhizal (AM) fungi form symbiotic relationships with plants, using their hyphae to enhance nutrient uptake and promote plant growth. Alternanthera philoxeroides, an invasive species, poses a significant threat to agriculture, forestry, and urban ecosystems in China. However, there is a lack of research on how AM fungi influence invasive plants under varying environmental conditions. This study explored the effects of two AM fungal strains and four substrate types on A. philoxeroides. The results showed that the mycorrhizal dependency of A. philoxeroides ranged from 6.09% and 37.21%. Plant height and root length of A. philoxeroides were primarily shaped by substrate quality. AM fungi significantly enhanced root and aboveground biomass, especially under nutrient-poor conditions. Leaf area increased in response to fungal inoculation, while leaf number was regulated by substrate nutrients. Overall, AM fungi promoted biomass accumulation, particularly when combined with nutrient-enriched substrates, underscoring their potential application in invasive plant management. Therefore, future management strategies should divide invaded areas into distinct control zones based on gradients of soil nutrient levels, with special attention given to key regions for targeted monitoring and prevention.