Premedication is often used to reduce the stress associated with anesthesia-related procedures. However, in some cases, patients may not cooperate with medication delivery because of significant fear and anxiety. We report a case of an uncooperative patient with severe intellectual disabilities who was successfully premedicated with the unique technique of sublingual midazolam administration using a suction toothbrush. The 38-year-old male patient was planned to receive dental treatment under deep intravenous sedation (IVS), but he refused both intravenous cannulation and mask induction. Preanesthetic medication delivery using other routes was attempted but not accepted. As the patient tolerated toothbrushing, we used repeated practice with sublingual water administration through the toothbrush's suction hole to gradually desensitize the patient. Using that same method, sublingual midazolam was administered as a successful premedication to allow placement of a face mask for inhalational induction without distress and completion of the dental treatment under IVS. For patients who refuse other premedication routes, sublingual administration during toothbrushing with a suction toothbrush may provide a successful alternative.