Recently, there has been a great interest in the application of multimodal hyperthermia. Hyperthermia, a controlled increase of temperature in tissues up to 42–45 °C, is a very promising anti-cancer medical treatment. Hyperthermia can be induced by means of ultrasound wave, alternating magnetic field, radiowave, laser light, etc. In our research, we combine magnetic hyperthermia with ultrasound thermal treatment to facilitate a more efficient, innovative sonomagnetic therapy. The experiments are performed using ultrasound phantoms doped with magnetic nanoparticles. These nanoparticles act like sonosensitizers and become the source of supplementary ultrasound attenuation which consequently leads to the increase of temperature. Because of their sensitivity to magnetic field they are also the source of heat in magnetic hyperthermia. In order to investigate the thermal effect of multimodal hyperthermia, phantoms are simultaneously irradiated with a focused ultrasound beam and exposed to the AC magnetic field. We demonstrate that this double thermal stimulation of phantoms doped with nanoparticles provides better heating efficiency which enables more precise control over the heating process. Magneto-ultrasonic heating creates more effective hyperthermia and has a big application potential in treating cancer at a lower magnetic particle concentration. The coupling of magnetic and ultrasonic hyperthermia gives the possibility for developing the new, innovative sonomagnetic thermal therapy.