Background: Erosion caused by carbonated beverages can reduce the surface microhardness of enamel and restorative materials. Adding calcium glycerophosphate (CaGP) to carbonated beverages may help mitigate these effects. Aims: To evaluate the effect of carbonated beverages with and without calcium glycerophosphate on the surface microhardness of enamel and glass ionomer cement (GIC). Materials and Methods: Twenty enamel blocks (2×3×4 mm) prepared from 10 extracted premolars and 20 GIC pellets (10 mm diameter, 2 mm height) were analysed. Initial surface microhardness was measured using a Vickers microhardness tester. Samples were divided into four groups: Group I: Enamel in carbonated beverage. Group II: Enamel in carbonated beverage with CaGP. Group III: GIC in carbonated beverage. Group IV: GIC in carbonated beverage with CaGP. Samples underwent immersion in solutions five times daily for 10 minutes, stored in artificial saliva between cycles, for seven days. Post-immersion microhardness was measured. Statistical analysis used: Paired and independent t-tests were applied. Results: Significant reduction in surface microhardness occurred in Groups I and III (p<0.001). Groups II and IV, with CaGP, showed no significant reduction. Conclusion: Adding 10mM CaGP to carbonated beverages effectively minimized surface microhardness loss in enamel and GIC.