Conservatism in accounting information can serve as a means to facilitate transactions between principals and agents by reducing agency costs. If agency costs are influenced by governance structures, the conservatism of accounting information aimed at reducing agency costs may manifest differently depending on governance structures. Therefore, examining the relationship between governance structures and the conservatism of accounting information can enhance our understanding of market pressure on accounting information and managers' accounting choices. In Anglo-American countries where ownership and management are separated, the agency problem between shareholders and professional managers can be a primary issue, and accordingly, professional managers' ownership stakes may influence the conservatism of accounting information (Lafond and Roychowdhury, 2008). However, La Porta et al. (1998, 1999, 2000) demonstrated through cross-country comparisons that in countries with weak legal protection for minority shareholders, expropriation of minority shareholders' interests by controlling shareholders may occur. In corporate environments such as Korea's, where family-centered owner-management prevails without separation of ownership and management, the agency problem between controlling shareholders and minority shareholders may be more significant. Therefore, this study examined the effects of governance and ownership structures on the conservatism of accounting information, focusing on family-managed firms. Specifically, it empirically investigated the conservatism of accounting information in cases where families both own and directly participate in the management of firms. Additionally, it analyzed how conservatism in accounting information changes according to the controlling family's ownership stake. Using a sample of 1,690 firm-year observations from non-financial firms with December fiscal year-ends continuously listed on the Korea Stock Exchange from 2005 to 2007, the empirical analysis could not confirm a consistent effect of family-managed firm status on the conservatism of accounting information. However, when ownership stakes were divided into intervals based on thresholds of 5%, 20%, and 50%, testing how conservatism in family-managed firms varies by ownership interval revealed that conservatism was strong in the interval of 50% or above, while it was relatively weak in ownership intervals below 50%. That is, conservatism in family-managed firms manifests differently depending on ownership stakes. Furthermore, parallelism tests conducted by dividing ownership stakes into four intervals also supported the results of this study, and results consistent with this study's findings were also obtained in samples excluding chaebol groups and business groups, confirming the robustness of the research results. These findings contrast with those of Wang (2006) and can be interpreted as controlling families, as suppliers of accounting information, providing more conservative accounting information as their ownership stakes increase due to alignment of interests with minority shareholders. This is because in the Korean context, where institutional protection for minority shareholders is relatively weak, conservatism is more likely to be determined by the suppliers of accounting information rather than by minority shareholders' demand for conservatism. Consequently, the results of this study support the alignment-of-interest effect, whereby the interests of controlling shareholders and minority shareholders converge as the controlling family's ownership stake increases.