Keratocystic odontogenic tumor is considered to be a benign cystic neoplasia of jaw bone with a higher rate of recurrence. It is noted to be third most common odontogenic cyst after radicular and dentigerous cyst. It has a peak incidence in the second and third decades of life and a gradual decline thereafter with a male dominance and has a considerable predilection for the posterior body of the mandible. Here is the case report of KCOT occurring in left mandible of 55 years old male patient. Key words- Keratocystic odontogenic tumor, neoplasia, odontogenic cyst