The influence of a ZrO2 addition (6 wt%) on the crystallization behaviour of a glass with potential for crystallization to Y3Al5O12-based glass-ceramics has been investigated. Differential thermal analysis, X-ray diffraction and scanning electron microscopy were used to assess the crystallization process. Vickers hardness was used to monitor changes in the crystallized volume fraction at different heat treatment temperatures. The results indicate that the addition of ZrO2 to the investigated glass composition promotes the formation of the y- Y2Si2O7 and inhibits the crystallization of the Y3Al5O12 phase