The present study aimed to evaluate the effect of universal adhesive pretreatment on the dentin bond strength of a resin-modified glass ionomer cement after radiotherapy. One hundred human third molars without caries were employed. One-half of the teeth were irradiated (total IR = 70.2 Gy). Both the irradiated and non-irradiated teeth were randomly divided into five groups (n = 10) according to dentin surface pretreatments: Single Bond Universal (3 M Oral Care), Gluma Bond Universal (Heraeus Kulzer), Prime&Bond Elect (Dentsply), Cavity Conditioner (GC) and control (no surface treatment). After Fuji II LC (GC) was bonded to the dentin surfaces, the specimens were stored for 7 days at 37 degrees C. The specimens were segmented into microspecimens, which were tested in the mu TBS device (1.0 mm/min). Failure modes were analyzed with stereomicroscope and scanning electron microscope. Data were analyzed using two-way ANOVA and Duncan tests (p = 0.05). The radiotherapy induced a decrease in the bond strength of Fuji II LC in all experimental groups (p < 0.05). All surface pretreatments increased the bond strength of Fuji II LC to non-irradiated and irradiated dentin (p < 0.05). The highest bond strength of Fuji II LC to irradiated dentin was obtained with Gluma Bond Universal, followed by Single Bond Universal and Prime&Bond Elect, then Cavity Conditioner (p < 0.05). The radiotherapy negatively influenced the bond strength of Fuji II LC regardless of surface pretreatments. The pretreatment with universal adhesives improved the bonding performance of Fuji II LC after radiotherapy.