Article investigates the effect of elevated temperature on properties of clinoptilolite blended cements. Clinoptilolite was used at 5 %, 10 %, 15 % and 20 % replacement by weight for Portland cement while sand and water quantities were kept constant in all mix designs. The mortars with 5 % or 10 % cliniptilolite substitution have compressive strength exceeding 42.5 MPa after being subjected to 400 °C and 500 °C.