A 25-year-old female visited to the hospital with a mass in right buccal area for 1 month. Mass excision was performed under local anesthesia via intraoral approach. The mass was conglomerated with many of 2-5 mm sized small clear cysts and located in the layer of buccal fat pad beneath buccinators muscle. The patient recalled the history of Botulinum Toxin Type A (Botox) injection on her face 6 months ago. Botox injection on face can cause pain, edema, ecchymosis, headache, eye brow ptosis, dry eye syndrome, drooling, mask face, nausea, malaise, or anaphylaxis. However, a mass caused by Botox injection has not been reported yet. The authors suggest the possibility of the formation of a mass from Botox injection through a foreign body reaction.