Introduction: Maintaining a vital pulp of immature permanent teeth is an essential and important requirement for dentin formation. Every effort must be made to preserve the vitality of teeth with incomplete apices to maintain the physiological apex generation process as much as possible. Pulpotomy is considered as one of the successful procedures to maintain this process in immature teeth. Aim: To evaluate the treatment success of pulpotomy of first immature molars with irreversible pulpitis using Platelet-Rich Fibrin (PRF) or Mineral Trioxide Aggregate (MTA) and monitoring the teeth for one year. Materials and Methods: A randomised clinical and radiological double-blinded evaluation was conducted in the Department of Paediatric Dentistry at Damascus University, Damascus, Syria. The research sample consisted of 24 first permanent immature molars in 20 children between age group of 6-8 years. Each of them had at least one first permanent immature molar with irreversible pulpitis. The research sample was randomly divided into two equal groups according to the treatment method: 1) pulpotomy with PRF; and 2) pulpotomy using MTA. Treatment were evaluated through periodic reviews and clinical and radiological examinations of the treated teeth by three specialists to assess treatment success. The treatment outcome was determined in terms of success or failure during two study periods (after six months and after one year). McNemar’s and Chi-square tests were applied using IBM SPSS version 20.0. The significance level was set at p-value <0.05. Results: Chi-square test showed that there were no statistically significant differences in the treatment success or failure between the treatment groups after six months and one year follow-up, p>0.05. After analysing the results statistically using McNemar’s test, it was observed that the treatment success rate after one year (50%, n=6) was lesser than that after six months (100%, n=12) in the MTA treatment group (p=0.031). In the treatment group using PRF, no significant difference (p=0.125) was observed in the success or failure of treatment between the two studied time periods (after six months and one year). Overall, the success rate of MTA was slightly higher than the success rate of PRF at the two study time periods (after six months and one year), the difference however was not statistically significant. Conclusion: Performing first immature molar pulpotomy using MTA had a slightly higher success rate than PRF pulpotomy.