Globally, the issue of soil contamination from heavy metals, polycyclic aromatic hydrocarbons (PAHs), and their composite contaminants is notably conspicuous. Microbial remediation technology, renowned for its low cost, environmental friendliness, and minimal secondary pollution, stands out as a promising soil remediation approach. However, its effectiveness is often hampered by factors such as nutrient conditions and the characteristics of pollutants. Humic acid, with its abundant active functional groups and unique chemical structure, holds considerable potential for enhancing microbial remediation of heavy metal and PAH-contaminated soils. Nevertheless, the application of humic acid raises concerns about potential adverse environmental effects. This article aims to succinctly review and analyze recent research progress in humic acid-enhanced microbial remediation of heavy metals and PAH-contaminated soils. It seeks to elucidate the mechanisms underpinning humic acid"s enhancement role and to conduct a comprehensive evaluation of the merits and limitations of humic acid-enhanced microbial remediation technology. Humic acid effectively reinforces microbial reduction of heavy metals and the biodegradation of PAHs through processes such as adsorption, chelation, and acting as a surfactant to enhance PAH solubility. However, caution is warranted, as humic acid might form recalcitrant compounds with pollutants, induce soil acidification, or reduce electron transfer rate, thereby impede microbial remediation. Future research should focus on developing robust assessment systems for humic acid-enhanced microbial remediation of heavy metals and PAH-contaminated soils. It should also explore the impact of humic acid on microbial metabolic expression and the production of functional proteins using advanced techniques such as metagenomics. This comprehensive approach will deepen our understanding of how humic acid influences microbial remediation in contaminated soils.