The production of flame retardant leather is significant for some leather types as aircraft and automotive upholstery leathers, and protective leathers as for motorcyclist jackets. For this reason, in this research it was aimed to modify effect of commercial flame retardant (CFR) on upholstery leathers treated with borax, boric acid and zinc borate. Control (group 1), 200 g/L CFR (group 2), 10 g/L borax + 60 g/L boric acid + 200 g/L CFR (group 3) and 10g/L zinc borate + 60 g/L boric acid + 200 g/L CFR (group 4) chemical solutions were applied to the leathers by padding finishing technique, and after the flame retardant application the leathers were finished with traditional finishing recipe. Flame retardant property of leathers was determined by vertical flammability (ISO 6941:2007) and limit oxygen index (LOI) (ASTM D 2863-77) fire resistance tests. In addition, the treated leathers were characterized by ATR-FTIR and SEM devices. According to LOI results, CFR CFR+borax+boric acid and CFR+zinc borate+boric acid treated groups of leather had 28.5%, 29.2% and 29.9% oxygen concentration respectively, while control sample had 27.0%. Flame retardant property of leathers was significantly enhanced by the effect of boron derivatives.