Neat and surface silanized barite (BR) was compounded with poly(lactic acid) (PLA) at the loading range of 5, 10, 15, and 20 wt% by melt blending process. Surface characteristics of BR samples were examined by infrared spectroscopy in attenuated total reflectance mode. Mechanical, thermal, water resistance, melt flow, and morphological characterizations of composites were performed by tensile and impact tests, dynamic mechanical analysis, water absorption test, melt flow rate (MFR) test, and scanning electron microscopy (SEM) analysis, respectively. BR additions lead to increase in tensile strength and modulus of PLA. The maximum improvement is obtained for 15 wt% of silanized BR containing composite. In contrast, percent elongation of PLA decreases with the incorporation of BR. Treated BR-loaded composites give higher impact energy values compared to untreated BR. Impact performance of composites increases with concentration. Silanized BR-filled composite at 5 wt% concentration exhibits higher storage modulus than unfilled PLA, where other composites yield relatively lower values in the case of storage modulus. Glass transition temperature of PLA extends to higher values by the addition of BR. Inclusions of BR samples cause a slight decrease in MFR of unfilled PLA. Water absorption of composites is found to be higher than that of PLA. Silanized BR-filled composites display lower water absorption values compared to untreated BR, thanks to hydrophobic nature of Si containing surface. According to SEM microimages of composites, more homogeneous dispersion in PLA matrix is achieved for treated BR particles than neat ones due to enhancement for interfacial adhesion of BR to PLA after silanization. [ABSTRACT FROM AUTHOR]