Background Collagenous fibroma or desmoplastic fibroblastoma is a rare benign fibrous tissue tumor. It usually presents as a painless, slowly growing mass. Collagenous fibroma arises ordinarily inside the subcutaneous tissues or skeletal muscles. Histopathologically, the tumor consists of scattered stellate and spindle cells in a hypovascular collagenous stroma without atypia or infiltration. The oral cavity is a very uncommon site for desmoplastic fibroblastoma. Only 15 published articles in the literature reported the intraoral location. We present a case of collagenous fibroma with a bilateral distribution on the hard palate. This is the second case of bilateral collagenous fibroma after a previously reported one in literature; however, our case was larger, occupying almost the whole palate. We discuss the management of this rare tumor and how we can reach definite diagnosis. Case presentation A 37-year-old Caucasian female patient had a huge bilateral firm palatal mass that caused breathing problems. There was no history of trauma and the patient had no relevant medical history Total surgical excision under general anesthesia was carried out and histopathological examination suggested a benign mesenchymal tumor. Immunohistochemistry was necessary to confirm the tumor origin and to exclude aggressive fibromatosis. A diagnosis of bilateral collagenous fibroma was reached. Six months after surgery, there was no recurring lesion and the patient’s health was good. Conclusions Collagenous fibroma is a benign fibrous tissue tumor of unknown cause that is treated with simple excision. The prognosis is good with no recurrence. Reaching an accurate diagnosis is mandatory to avoid aggressive treatment since collagenous fibroma may be misdiagnosed as aggressive fibromatosis in case of massive size. Clinicians and pathologists should be aware of this unusual tumor for conservative management without side effects.