Aim: To test 3D-printed immobilization devices for future use in magnetic resonance-guided focused ultrasound hyperthermia. Material & methods: Using a surface scanner, patient-specific pelvic immobilization devices were 3D printed. The setup reproducibility was measured both on linear accelerator (LINAC) and magnetic resonance. An ultrasound imaging probe was used to acquire reference images and later to acquire images once attached into the embedded holder. Results: Prepositioning accuracy was tested at LINAC using an optical surface monitoring and MRI and showed submillimeter accuracy and small angular rotations. Agreement was high between the ultrasound reference images versus the immobilized probe. Conclusion: Reported results are considered as a promising step toward a fast and precise positioning of patients and an easier integration of radiotherapy and magnetic resonance-guided focused ultrasound hyperthermia.