Poly (lactic acid) (PLA)-based biocomposites containing flax fiber (FF) and basalt fiber (BF) both separately and together were prepared by melt blending method at the total constant ratio of 30 wt%. Mechanical properties, thermo-mechanical characteristics, thermal stability, flow behaviors, water uptake, and morphology of composites were investigated by tensile, hardness and impact tests, dynamic mechanical analysis (DMA), thermal gravimetric analysis, melt flow index (MFI) test, water absorption, and scanning electron microscopy, respectively. Mechanical test results show that tensile strength, elongation, elastic modulus, and impact strength are extended up to higher values with increase in BF content in hybrid composites. Conversely, the presence of FF displays a negative effect in which these values drop down drastically as the FF concentration increases. On the other hand, slightly higher hardness values are obtained by the addition of FF at higher loadings. DMA analysis reveals that BF inclusion leads glass transition temperature of PLA to one point higher, but hybrid and FF containing composites shift that temperature to lower values. Storage moduli of composites are enhanced with the increase in BF concentration and remarkable decreases are observed for FF-filled composites. Hybrid composites exhibit average MFI values between PLA/FF and PLA/BF composites.