The creation of thermostable, flame-retardant, mechanically robust bioplastics is highly desirable in the industry as one sustainable alternative to traditional petroleum-based plastics. Unfortunately, to date there lacks an effective strategy to endow commercial bioplastics, such as polylactide (PLA) with such desired integrated performances. Herein, we have demonstrated the fabrication of a novel MXene-phenyl phosphonic diaminohexane (MXene-PPDA) nanohybrid via the intercalation of PPDA into the MXene interlayer. The interlayer spacing of MXene nanosheets is enlarged and as-prepared MXene-PPDA is homogeneously dispersed in the PLA matrix. Incorporating 1.0 wt% MXene-PPDA enables PLA to achieve a UL-94 V-0 rating, with a ∼22.2% reduction in peak heat release rate, indicating a significantly improved flame retardancy. Meanwhile, the 1.0 wt% MXene-PPDA also increases the initial decomposition temperature of PLA composite, giving rise to a ∼25-fold enhancement in char yield relative to pure PLA. Additionally, the MXene-PPDA enhances the toughness while retains the mechanical strength for PLA. This work offers an innovative strategy for the design of multifunctional additives and the creation of high-performance polymers with high thermal stability, mechanical robustness and low flammability, expecting to find many practical applications in the industry.