This paper investigates residual thermal and mechanical properties of high-performance fiber-reinforced cementitious composites (HPFRCCs) proportioned with high-volume fly ash after exposure to 200, 400, 600, and 800 °C. The investigated thermal and mechanical properties include the thermal conductivity, specific heat, compressive strength, tensile strength, tensile ductility, and density. The effects of five mix proportioning variables on the material properties are evaluated, which include the water-to-binder ratio (0.24-0.36 by mass), sand-to-binder ratio (0.36-0.66 by mass), fly ash content (60%-75% by mass), polyvinyl alcohol fiber content (1.5%-2.2% by volume), and superplasticizer content (0.10%-0.15% by mass). Experimental results reveal significant dependence of the residual thermal and mechanical properties on temperature and the mix proportion, which can be attributed to a series of chemical and physical reactions that occur at elevated temperatures. This study can facilitate optimization of mix proportions of HPFRCCs for enhanced thermal and mechanical performance in fire or high temperature applications.