Commercial β‐SiAlON ceramics were joined using mixed Si3N4, Y2O3, Al2O3, and SiO2powders. At a joining temperature of 1600°C and a hold time in excess of 10 min, the adhesive was converted to an approximate 60:40 vol% composite of β‐SiAlON–glass‐ceramic. The grain size of the acicular β‐SiAlON grains precipitated in the joint (submicrometer diameter, average aspect ratio of 10) was significantly smaller than those in the adherend ceramic (1–5 μm diameter). Intergrowth of β‐SiAlON grains at the joint interface resulted in high bond strengths. The chemistry and microstructure of the ceramic adhesives