Medium-sized vestibular schwannomas are those that occupy the cerebellopontine angle, in other words, the degree T3 tumors according to the Matties and Samii classification, as well as grade III of the Koos classification. Medium-sized vestibular schwannomas can be treated with microneurosurgical excision stereotactic radiosurgery, or observation. The retrosigmoid approach with transmeatal access serves is the basis for microneurosurgical resection. This chapter provides a detailed description of the microneurosurgical anatomy of the cerebellopontine angle and the stages of the retrosigmoid approach. We review the selection of the most appropriate treatment technique for each patient, along with its results, outcomes, and complications. Medium-sized vestibular schwannomas are the most prevalent in the microneurosurgical practice. The goal of treatment is to maintain the facial nerve function, and all treatment modalities have a reasonable functional prognosis.