The public prosecutor’s office, as a core pillar of the criminal justice system, plays a decisive role in implementing criminal policy and achieving justice. Yet prosecutorial decisions in prosecution and investigation cannot be explained solely through formal legal rules; they emerge from the interaction of institutional structures, functional demands, and societal needs. Using an analytical-descriptive method, this study examines the relationship between utilitarian theory and the logic shaping prosecutorial decisions. It explains the foundations of classical and revised utilitarianism, analyzes the role of instrumental rationality in criminal decision-making, and identifies its operational manifestations in Iran’s prosecutorial system. Findings show that despite theoretical emphasis on public interest, a centralized structure, lack of institutional separation, and dominance of quantitative approaches hinder the utilitarian function of the prosecutor’s office in addressing social problems. Moreover, the absence of an outcome-based evaluation system and weak links with support institutions reduce its capacity to confront emerging criminological challenges. Strengthening performance assessment, fostering institutional independence, and integrating social support mechanisms could enhance its responsiveness to evolving criminal phenomena while aligning decisions more closely with utilitarian principles.