The objective of the study was to determine the therapeutic efficacy of early combined treatment with intratympanic steroid injection (ITSI) in patients with severe to profound sudden sensorineural hearing loss (SSNHL), who did not respond to initial systemic steroid treatment (SST). The study design included historical controlled trials (retrospective analysis for the SST group). Patients (n = 73; 38 women and 35 men) diagnosed with severe to profound SSNHL at the time of their first visit in tertiary referral centers were recruited. Among these 73 patients, 30 patients who showed no early response within a week after the start of initial SST were prospectively included as the ITSI group. ITSI was performed twice a week for two consecutive weeks. In contrast, 43 patients with the same condition who did not receive ITSI were retrospectively included as the SST group. For each group, pure-tone audiogram (PTA) and speech discrimination score (SDS) tests were performed before SST and more than 2 months after termination of treatment in each group. After termination of each treatment, the final average gain on PTA showed no significant difference between the two groups; however, the final average gain of SDS demonstrated a significantly better recovery in the ITSI group. ITSI as part of an early combined therapy represents an effective treatment in terms of the improvement of SDS in severe to profound SSNHL showing no early response to initial SST.