A spar cap assembly for a jointed rotor blade of a wind turbine includes a root spar cap assembly and a tip spar cap assembly. The root spar cap assembly includes a root tensile spar cap and a root compressive spar cap, and is formed from a first composite material. The tip spar cap assembly includes a tip tensile spar cap and a tip compressive spar cap, and is formed from a second composite material that is different from the first composite material. The thickness of a joining end of the root tensile spar cap is different from the thickness of a joining end of the tip tensile spar cap, and the thickness of a joining end of the root compressive spar cap is different from the thickness of a joining end of the tip compressive spar cap.