Owing to the growing environmental pressure to reduce waste and pollution, the effective utilization of industrial solid wastes in construction applications has gained notable attention. This study investigates the mechanical and thermal properties of cement mortars incorporating two types of waste slags. Ferrochrome (FeCr) slag aggregate was used as a replacement for sand at the ratios of 25, 50, 75 and 100 wt. %. Ground granulated blast furnace slag (GGBS) has been used as a partial replacement of cement at the ratio of 25 wt. %. Compressive strength, permeable voids content and thermal conductivity tests have been conducted after 28 days of curing. The microstructure characteristics have been investigated by scanning electron microscope (SEM) equipped with energy dispersive analytical x-ray unit (EDAX). The experimental results revealed that FeCr waste aggregates could satisfactorily replace for natural fine sand in cement mortars up to 25 wt. % without a remarkable degradation of the compressive strength. Furthermore, Increasing replacement ratios of FeCr aggregates over 25 wt. % have resulted in noticeable decrease in thermal conductivity and an increase in the permeable voids content of cement mortars. The integration of GGBS with FeCr aggregates leads to enhanced compressive strength, reduced voids content and contribute to improved microstructure. The developed mortars with comparatively improved thermal resistance can be recommended for several structural and non-structural applications especially in hot weather regions.