This study explores the effects of interactions among key stakeholders, i.e., auditors, underwriters, and firm owners on IPOs’ first-day returns in selected OECD nations. It also examines the alteration effects of legal origin (Common law and Civil law) on the relationship between the interacted key stakeholders and IPOs’ first-day returns. A total of four thousand one hundred and sixty-four IPOs from twenty-eight OECD nations are included in this study. Since it is cross-sectional data, a two-stage least square regression is applied. The empirical outcomes indicate that, in general, the interacted reputable underwriters and auditors have a positive impact on IPOs’ first-day return. The relationship is modified between common law and civil law nations, whereby in civil law nations, no significance is demonstrated except for the interaction between the reputable auditors and underwriters. In the common law nation, interactions between reputable auditors and ownership retention have an impact on IPOs’ first-day return. The research findings provide outlooks into an IPO framework for issuers, investors, and regulators. Issuers may want to weigh carefully the costs and benefits of hiring credible auditors and underwriters when going public as they act as signaling agents. As for the investors, they should take into consideration the involvement of reputable underwriters and auditors and the degree to which the IPO firms retain ownership, as the interactive effects give clear signals on firm valuation and IPOs’ first-day returns. Regulators may find the findings informative concerning the creation of a more organized regulatory and financial system that could lead to a deeper and more open financial market.