Abstractα‐SiAlON is well known for its excellent mechanical properties, but its thermal properties are less investigated. In this work, we investigate the thermal conductivity of Ca α‐SiAlON ceramics with varying m and n values and prepared samples by spark plasma sintering (SPS) at 1600°C or gas pressure sintering (GPS) at 1800°C and 1900°C. The prepared Ca α‐SiAlON ceramics showed thermal conductivities ranging from 4.6 to 10.7 W/(mK) at 25°C. It was found that the thermal conductivity of the α‐SiAlON samples could be reduced by increasing either m or n or both. Besides, the samples prepared by SPS had lower thermal conductivity compared with those by GPS due to their smaller grain size, and the effect of m and n would be minor after m reached 2. These results provide basic knowledge for tuning α‐SiAlON's thermal conductivity for applications concerning thermal management.