Background: Radiotherapy is a key treatment for head and neck cancers but often compromises oral health, partly through its impact on restorative materials. A specific concern is whether ionizing radiation alters the water absorption and solubility of fluoride-releasing restoratives, potentially affecting their durability. This study aimed to evaluate these properties following clinically relevant radiation exposure. Methods: Seven contemporary fluoride-releasing restorative materials (Fuji IX, Equia Forte HT, Fuji Triage, Activa Presto, Cention, Luminos, and Beautifil II) were tested (n = 10 per group). Specimens were either irradiated with 70 Gy in 35 fractions using a clinical linear accelerator or maintained as non-irradiated controls. Water absorption and solubility were measured over 35 days according to ISO 4049 protocols, and data were analyzed with repeated-measures ANOVA. Results: Across all materials, irradiated specimens exhibited slightly higher water absorption and solubility values compared to controls; however, differences were not statistically significant (p > 0.05). Material-specific trends were observed, with Fuji IX, Fuji Triage, Beautifil II, and Equia Forte showing relatively higher absolute values. Conclusions: Clinically relevant ionizing radiation did not significantly affect the water absorption or solubility of the tested fluoride-releasing restorative materials, suggesting preserved physicochemical stability under therapeutic conditions.