Background: Glass ionomer cements (GIC) have excellent biocompatibility and fluoride release properties; however, they suffer from moisture sensitivity and low mechanical properties. Calcium chloride (CaCl2) in solution form improved the surface hardness of GIC. Some authors suggested the preparation of a new formulation of CaCl2 to be more stable in application. Surface hardness was measured at baseline and after pH-cycling protocol. Aim of the study: to evaluate the effect of CaCl2 application in both solution and gel forms on the surface hardness of the GIC at baseline and after pH cycling. Materials and Methods: Thirty disc-shaped specimens were prepared from Fuji IX GIC and divided into three groups according to different surface treatments, (n=10); group 1 (control), group 2 (CaCl2 solution) and group 3 (CaCl2 in gel form). pH-cycling protocol was done for all specimens using 5% acetic acid (pH=3) twice /day, rinsed, dried and then stored in distilled water. This cycle was repeated for 14 days. Surface hardness was measured at baseline and after pH-cycling. Results: At baseline and after pH-cycling, the control group showed the lowest mean hardness. Two other CaCl2 gel and CaCl2 sol. showed insignificant differences between each other. pH-cycling resulted in a significant decrease in surface hardness in all groups compared to baseline. Conclusions: Both CaCl2 forms improved surface hardness of self-setting GICs. Yet, handling of gel-form was easier. pH-cycling protocol deteriorated surface hardness values of all groups.