In the current study, huntite hydromagnesite (HH) was used as flame retardant additive in poly (lactic acid) (PLA) to produce green flame retardant composites. The effects of HH amount, particle size and surface modifications on the flame retardant, thermal and mechanical properties were investigated. The properties of the composites were investigated using limiting oxygen index (LOI), horizontal and vertical burning test (UL 94), mass loss calorimeter, thermogravimetric analysis, tensile test, impact test and dynamic mechanical analysis. According to results, the flame retardant PLA composites with different UL-94 ratings (HB, V2, V0) were produced. The LOI value increased as the added amount of HH increased. The highest LOI value of 34.2 was achieved with the addition of 60 wt% HH. Surface modifications had no remarkable effect on the flammability properties of the composites. The addition of HH reduced the tensile and impact strengths and improved the elastic modulus of the composites as the added amount of HH increased. The addition of HH with large particle size deteriorated the flammability properties and tensile strength despite of the increase in impact strength. Surface modifications improved the mechanical properties of the composites due to the improvement in interfacial adhesion between HH and PLA.