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, endowed with numerous active functional groups and a distinctive chemical structure, significantly boosts the microbial reduction of heavy metals and the biodegradation of PAHs. It facilitates these processes through adsorption and chelation, effectively reinforcing microbial reduction of heavy metals and the biodegradation of PAHs and acting as a surfactant to enhance PAH solubility. Moreover, it acts as electron shuttles, facilitates microbial respiration and provides energy sources for microorganisms, thereby enhancing the bioreduction of heavy metals and the biodegradation of PAHs in soil. However, attention is needed as humic acid may also interact with pollutants to create persistent compounds, contribute to soil acidification, or diminish the rate of electron transfer, potentially obstructing microbial remediation 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. Future researches should focus on developing robust assessment systems for humic acid-enhanced microbial remediation of heavy metals and PAH-contaminated soils. The impact of humic acid on microbial metabolic expression and the production of functional proteins should also be explored using advanced techniques such as metagenomics. These comprehensive approaches will deepen our understanding of how humic acid influences microbial remediation in contaminated soils.