Aim: It is to evaluate using of Platelet Rich Fibrin (PRF) And Calcium Hydroxide as a pulpotomy agent. Subjects and Methods : The present study was carried out on 9 adult healthy mongrel dogs which classified into 3 equal groups. Under general anesthesia, by means of split-mouth technique the dog's mandibular teeth were used. After the period of study, the animals were sacrificed by overdose of thiopental sodium and the lower jaw was excised with a bone saw. The study was carried out under the histological evaluation of cellular and pulp tissue response using H&E stains. Results: The result of the present study revealed that, the early response of pulp tissue to all tested materials was inflammatory reactions, of various degrees, that were subsided by time completely only in PRF group. PRF has a powerful agent for regenerative effect on pulp tissue in an absence of dentin bridge formation. It also showed that, the PRF was well tolerated by pulp tissue of dogs' teeth. On the contrary, pulp degeneration and necrosis were the end results of pulpotomy with Calcium hydroxide agent. Conclusion: PRF can be more reliable than Calcium hydroxide in pulpotomy. PRF is the new material of choice that could be used as alternative to calcium hydroxide in pulpotomy.