This paper presents a brand new hybrid material on the nanometric scale: the antimony sulfoiodide (SbSI) within carbon nanotubes (CNTs). It was prepared in CNTs ultrasonically by using elemental antimony (Sb), sulfur (S) and iodide (I) in the presence of methanol under ultrasonic irradiation (34 kHz, 2.6 W/cm2). The sonochemical process was leaded for 3 hours at 323 K. The antimony sulfoiodide (SbSI) consisted in multiwalled carbon nanotubes (CNTs) were characterized high-resolution transmission electron microscopy (HRTEM). These investigations exhibit that the SbSI filling the CNTs has single-crystal structure in nature and in the form of multiwalled carbon nanotubes. The SbSI grown in CNTs are very promising materials for further investigations as well as for some industrial and medical applications.