We have investigated 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. Dry weights, flexural strengths, and compressive strengths of specimens were determined as a function of time. The same properties were again evaluated after specimens, having reached the age of 90 days, were exposed to 300 °C, 400 °C and 500 °C temperatures for 3 h. Initial setting times for all cements prepared were ≥ 60 minutes, the limiting time according to TS EN 197-1. The mortars with 5 % or 10 % cliniptilolite substitution have compressive strength exceeding 42.5 MPa after being subjected to 400 °C and 500 °C.DOI: http://dx.doi.org/10.5755/j01.ms.22.4.13354