The objective of this study was to assess the effect of heat application on the mechanical properties of glass ionomer cements. experimental design. The effect of heat on glass ionomer cements during their setting was evaluated by measuring compressive strength, flexural strength and microhardness. Moroever, temperature changes from one surface of the glass ionomer cement specimens 2, 4, and 6 mm thick to the other surface were measured. A condensable glass ionomer cement (Fuji IX) and a ceramic-reinforced glass ionomer cement (Amalgomer CR) were used as test materials. Heat was applied with soldering iron for 2 minutes at 80±2oC. All mechanical tests were carried out 24 hours after the setting of glass ionomer cements. No significant differences in compressive strength were found between the control groups and the heated groups. There were no statistically significant differences in the flexural strength value for both groups of Fuji IX. On the contrary, when heat was applied to Amalgomer, its mean flexural strength reached a value that was higher than that of Amalgomer control. Significant differences in microhardness were found between the control groups and the heated groups and between Fuji IX and Amalgomer CR. Temperature rising in both glass ionomer cements was also noted. two-way ANOVA was used where appropriate and independent samples t-test was used in case of interaction. It is established that heat application improved the surface mechanical properties of conventional glass ionomer cements.