The purpose of this study is to conduct a comparative analysis of the nature and legal effects of conditional and unconditional bank guarantees in Iranian law and to compare them with international standards, adopting a legal and practical approach. This research is conducted using an analytical–comparative approach. To this end, the theoretical and conceptual foundations of bank guarantees are first examined based on Iranian domestic law and doctrinal analyses. Subsequently, relevant regulations, banking practices, and judicial decisions are analyzed. In the next stage, international standards—particularly the URDG 758 Rules—are studied as a comparative model and evaluated in relation to the Iranian legal system. The findings indicate that conditional bank guarantees, due to their dependence on the underlying contract and the possibility of judicial intervention, have a weaker guarantee function. In contrast, unconditional bank guarantees, which are based on the principle of independence, constitute a more effective instrument for securing obligations when properly recognized. However, under Iranian law, the lack of explicit legislative recognition of the principle of independence and the limited formulation of the fraud exception have led to the practical weakening of this type of guarantee. The study concludes that enhancing the effectiveness of bank guarantees in Iranian law requires explicit recognition of the independent nature of unconditional bank guarantees, restricting judicial intervention to cases of manifest fraud, and selective harmonization with international standards. Such an approach can significantly improve legal certainty, predictability, and the confidence of economic actors.