The crystallization mechanism and properties of diopside (CaMgSi 2 O 6 )/anorthite (CaAl 2 Si 2 O 8 ) hybrid glass-ceramics fabricated from a CMSA (CaO-MgO-SiO 2 -Al 2 O 3 ) glass system were studied as a function of Al 2 O 3 additions. The parent glass prepared was pressed to pellets isostatically and was sintered to produce glass-ceramics. A non-isothermal analysis was performed to study the crystallization behavior of diopside/anorthite hybrid glass-ceramics using differential thermal analysis (DTA) with various heating rates (5-20 K min Γ 1 ) and John-Mehl-Avrami and Kissinger equations. The occupying ratio of diopside and anorthite phases, crystal identification and microstructure in the glass-ceramics containing various Al 2 O 3 contents were analyzed. Also the thermal conductivity and density of diopside/ anorthite composites were measured to apply to LED packaging materials. The main crystalline phases for CaO-MgO-SiO 2 -Al 2 O 3 glass-ceramics system containing 8.6 wt% or less Al 2 O 3 , and 15.9 wt% or more Al 2 O 3 were the diopside and anorthite, respectively. The difference (DT) of initiation temperature for crystallized (T x ) and glass transition temperature (T g ), calculated from the DTA curve for a glass is inversely proportional to the density of glass-ceramics fabricated from the glass. The highest crystallization temperature was 946 1C for the glass-ceramics containing 27.4 wt% Al 2 O 3 , which is low enough to apply the LTCC process. The glass-ceramics of diopside base with no Al 2 O 3 added had the highest thermal conductivity of 2.372 W/m 1C among all specimens fabricated in this study.