OBJECTIVE To prevent cavity problems in canal wall down mastoidectomy, silicone block for mastoid obliteration was used. METHODS In this retrospective cohort study, 39 patients (21 males and 18 females) underwent canal wall down mastoidectomy and mastoid obliteration using silicone block. We evaluated the postoperative outcome, the time until epithelialization of the cavity, graft success rate, and the hearing outcome. RESULTS The time until complete epithelialization of the mastoid cavity was 35.5 ± 5.4 days. We had a graft success rate of 100% during the follow-ups. The postoperative evaluation revealed 36 dry ears (92.3%) patients without any cavity problems. However, one ear developed granulation tissue, and two ears had partially exposed silicone block, which required revision mastoidectomy. Regarding hearing outcomes, a complication such as deaf ear was not reported. CONCLUSIONS Silicone block is safe and suitable for mastoid obliteration and external auditory canal reconstruction in canal wall down mastoidectomy. METHODS 4.