The flammability and mechanical properties of Al(OH)(3)/BaSO4/polypropylene (PP) composites were investigated. The flow, morphological, and thermal properties were also analyzed by melt flow index (MFI), Scanning electron microscopy (SEM), and Differential scanning calorimeter (DSC) studies, respectively. Total filler amount was fixed at 30 wt % to optimize physical characteristics of the composites. In addition to the flame retardant filler Al(OH)(3), BaSO4 was used to balance the reduction in impact strength at high filler loadings. Substantial improvement in mechanical properties was achieved for 20 wt % Al(OH)(3) (i.e., 10 wt % BaSO4) composition while maximum flammability resistance was obtained for 30 wt % Al(OH)(3) composite. SEM studies showed that the presence of aggregated Al(OH)(3) particles led to low interfacial adhesion between them and PP matrix ending up with decreased mechanical strength. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 3034-3040, 2010