The emergence of smart contracts as self-executing programs based on blockchain technology has created fundamental challenges for the application of the principle of good faith in contract law. This article, using a descriptive-analytical method and library resources, examines the scope of good faith in smart contracts across three legal systems: Imamiyyah Jurisprudence, Iranian Law, and European Union Law. The main question is how the obligation to observe good faith, which in traditional law extends to all stages of contractual life, can be applied in contracts based on immutable and self-executing code. The research findings indicate that the European Union, through the adoption of the "Data Act" (2023) and the requirement to provide emergency stop mechanisms and transparency, has taken initial steps toward regulating this phenomenon. In Imamiyyah Jurisprudence, principles such as "lā ḍarar" (no harm), "ghurūr" (deception), "amānah" (trustworthiness), and "khiyār al-ʿayb" (option of defect), as well as attention to the higher objectives of Sharia (maqāṣid al-sharīʿah), provide significant capacity for flexibility against the requirements of smart contracts (Soualhi et al., 2024, p. 8; Yaqin et al., 2026, p. 15). Despite the lack of specific legislation, Iranian law has the possibility of recognizing these contracts by referring to Article 10 of the Civil Code and the Electronic Commerce Law, but there are serious challenges regarding the application of good faith in the stages of negotiation, conclusion, and execution. The article concludes that by utilizing the capacities of Imamiyyah Jurisprudence and the experience of EU law, a native model can be presented for applying the principle of good faith in smart contracts in Iranian law.