Background: The aim of this study was to evaluate six different glass ionomer cement (GIC)-based restorative materials through comparisons of microleakage and fluoride release. Materials and Methods: For microleakage, 30 teeth were randomly separated into 6 groups of 5: Group 1 (Dyract: compomer), Group 2 (Freedom: compomer), Group 3 (Equia: high-viscosity glass ionomer cements), Group 4 (Fuji IX: resin-modified glass ionomer cement), Group 5 (Ketac Molar: traditional glass ionomer cement [TGIC]) and Group 6 (Voco: TGIC). For fluoride release of six different GIC-based restorative materials, standard samples were prepared of 4 mm thickness and 7 mm diameter. A total of 60 samples were obtained as 10 samples from each group. The analyses were made using a Thermo Orion 720 A+ ionometer with the Orion fluoride electrode. At the end of 24 h, 72 h, 7 days, 14 days, and 30 days, the electrode was placed into the dish containing the sample, distilled water, and TISAB II; a reading was taken; and the value shown on the screen was recorded. Results: For microleakage, a statistically significant difference was determined between the groups in respect of the occlusal variable (P < 0.05), no statistically significant gingival variable (P 0.05). About fluoride release: According to the repeated measures variance analysis results, the difference between the groups, and between the time-group interaction and according to time, was found to be statistically significant (P < 0.05). Conclusions: In terms of microleakage, it was concluded that all materials could be used in clinical applications. The Equia high-viscosity glass ionomer cements (HVGIC) was determined to be the material with the highest fluoride release value.