Nowadays, the amount of chrome-tanned leather scraps from the leather industry is increasing rapidly due to diminishing interest in their utility in related areas. These kinds of wastes cause considerable negative, environmental effects, and therefore, producers should find new methods of recycling and/or disposal. It is speculated that leather scraps may be a valuable additive in rubber-based materials thanks to their similar elastic properties. In this study, chrome-tanned leather wastes have been incorporated into natural rubber and styrene-butadiene rubber and their blends in various ratios by using a Banbury mixer and two-roll mill, subsequently. Effects of the wastes on rheological, thermal, mechanical, aging, and morphological properties of the blends were investigated. Different penetration ability and distinct cure rates of the two rubbers caused interesting rheological characteristics. Original mechanical properties of styrene-butadiene rubber and its blends were retained after waste incorporation. Furthermore, thermal aging resistance of natural rubber matrix could be improved. The most significant effect of leather particles is the enhancement of the tear strength of all the vulcanizates by shifting the tear mechanism towards the tortuous fracture pathway.