Prolongation of criminal proceedings is one of the most serious challenges facing criminal justice systems, as it undermines the realization of fair and efficient trial standards. This phenomenon is neither limited to a specific legal system nor to a particular historical period; rather, it arises from a combination of structural, human, and procedural factors throughout different stages of criminal proceedings. This article adopts an analytical–descriptive approach to examine stage-specific causes of delay in the Iranian criminal justice system, focusing on the phases of prosecution and investigation, trial and adjudication, and enforcement of criminal judgments. By distinguishing between general and stage-oriented factors, the study concentrates on deficiencies that uniquely affect each phase of the process. Key causes include the concentration of prosecutorial and investigative powers within the prosecution office, challenges to judicial impartiality, inefficiencies in judicial delegation procedures, irregular attendance of judges, improper scheduling of hearings, and administrative shortcomings in the enforcement stage. The findings indicate that a significant portion of procedural delay stems from structural weaknesses and inadequate performance of judicial and administrative personnel. Such delays conflict with the principles of Islamic criminal jurisprudence, which emphasize prompt dispute resolution and timely justice, thereby highlighting the necessity of structural, managerial, and procedural reforms within the criminal justice system.