Hearing loss is a worldwide problem. Sensorineural hearing loss (SNHL) is the most common sensory deficit. In mammals, hair cells and auditory neural cells are terminal cells that can regenerate after damage, rendering SNHL a permanent problem. The current solutions for SNHL include hearing aids, cochlear implants and hearing assisting devices. Stem cell therapy provides hope for replacing damaged hair cells and auditory neural cells. There are three basic types of stem cells: embryonic stem cells, induced pluripotent adult stem cells, and mesenchymal stem cells. Mesenchymal stem cells represent an interesting choice in stem cell therapy. There are many parameters that affect the outcome of stem cell therapy for hearing loss. The in-vivo animal research regarding stem cell therapy for hearing loss is heterogeneous regarding those parameters. This article explores stem cell therapy in hearing loss in general, focusing on mesenchymal stem cells, which are the most used stem cell type.