This study rigorously analyzes the legitimacy of plea bargaining in Tanzania, as delineated in the Criminal Procedure Act Cap 20. Additionally, the article examines the whole bargaining process in criminal cases. Plea bargaining is used to facilitate the prompt resolution of criminal cases. Plea bargaining is intended to shun complicated court proceedings; to reduce the congestion in the prisons in Tanzania; to save time and cost of the government revenues. Despite the good reasons, the plea bargaining is still faced by several challenges. It is considered that the plea bargaining is sometime contrary to the whole process of fair trial. There are number of concerns confronting the constitutionality of the plea bargaining process in Tanzania. Observing presumption of innocence is a challenge during plea bargaining process. Plea agreement leads to criminal records on the accused. In some circumstances the accused may plead guilty due to fear of long and complex court trial. This type of plea can be said to be involuntarily obtained hence contrary to the constitutional principle of presumption of innocence. Further, there is no room of establishing the burden of proof; proper investigation process and so many other challenges. This paper addresses the challenges on plea bargaining in details. The paper also provides the measures to be taken to ensure that the plea bargaining is applied towards the fair dispensation of criminal justice in Tanzania.