As the demand for environmentally friendly materials continues to rise, poly(lactic acid) (PLA) has emerged as a promising alternative to traditional plastics. The present review offers a comprehensive analysis of the biodegradation behavior of PLA in diverse environmental settings, with a specific focus on soil, compost, water, and wastewater environments. The review presents an in-depth comparison of the degradation pathways and kinetics of PLA from 1990 to 2024. As the presence of different microorganisms in diverse environments can affect the mechanism and rate of biodegradation, it should be considered with comprehensive comparisons. It is shown that the mechanism of PLA biodegradation in soil and compost is that of enzymatic degradation, while the dominant mechanisms of degradation in water and wastewater are hydrolysis and biofilm formation, respectively. PLA reveals a sequence of biodegradation rates, with compost showing the fastest degradation, followed by soil, wastewater, accelerated landfill environments, and water environments, in descending order. In addition, mathematical models of PLA degradation were reviewed here. Ultimately, the review contributes to a broader understanding of the ecological impact of PLA, facilitating informed decision-making toward a more sustainable future.