Radicular cysts are the most common odontogenic cysts affecting the oral cavity. They are usually asymptomatic and are diagnosed during routine radiologic examination. Depending on the extent of the lesion, the cyst is managed by non-surgical or surgical means. Root canal therapy is preferred in a localised lesion whereas in large extensive cysts, enucleation, marsupialization or decompression is done. In this case report, we present the diagnosis and surgical management of a massive infected radicular cyst in the maxillary posterior region.