We examine a firm’s decision to choose between an equity spin-off and a captive spin-off and the decision’s announcement effect. A captive spin-off, which is a unique form of corporate divestiture in Korea and a few other countries, differs from an equity spin-off in that the spun-off entity remains a wholly owned subsidiary of the parent company and shareholders cannot directly hold ownership stakes in the subsidiary even after the spin-off. On the other hand, in the case of an equity spin-off, which is prevalent in many developed countries such as the U.S., incumbent shareholders receive proportional ownership in the spun-off entity, which typically becomes a publicly listed company after the spin-off. It is well-documented that corporate spin-offs can be beneficial to shareholders because they are likely to reduce negative synergies via refocusing, mitigate information asymmetry, and address relevant agency issues. However, many practitioners in Korea have criticized captive spin-offs, arguing that they can be detrimental to minority shareholders because the controlling owner can decide the spun-off entity’s eventual disposal without shareholder intervention. Despite the notable differences between these two spin-off methods, little has been examined regarding the determinants of firms’ spin-off method choices. We examine a large sample of Korean spin-offs, including both equity and captive spin-offs, from 1998 to 2022. Note that, in our sample, captive spin-offs account for 75.6% (704 spin-offs) of all spin-off activities in Korea, whereas equity spin-offs account for only 24.4% (227 spin-offs). This prevalence of captive spin-offs highlights the importance of our study examining what motivates a firm to choose such a controversial spin-off method. Examining simple mean differences between the two types of spin-offs, we find that captive spin-offs are preferred to equity spin-offs by firms that are smaller, less profitable, younger, investing more, and paying out less. These differences suggest that a firm’s choice of spin-off method can be driven by factors other than agency issues. In our multivariate analysis, we find evidence that a firm’s decision to choose between the two spin-off methods can be affected by market valuations. Specifically, an average parent firm is more likely to choose captive spin-off when it is overvalued relative to its industry peers, whereas it is more likely to choose equity spin-off when it is undervalued relative to its peers. Similarly, firms in overvalued industries are more likely to choose captive spin-offs, while those in undervalued industries are more likely to choose equity spin-offs. Moreover, firms with high growth rates and low cash flows, i.e., those likely in need of capital infusion, are more likely to choose captive spin-offs. Examining market reactions to spin-off announcements, we find that equity spin-off announcements, on average, attract more favorable market reactions in terms of announcement period cumulative abnormal returns than those of captive spin-offs. Further analysis reveals that the average announcement return is highest among undervalued parent firms that chose equity spin-offs, and the return is lowest among overvalued firms that chose captive spin-offs. Also, in the case of the former, announcement returns are on average higher when the spun-off entity is smaller relative to the parent, whereas in the case of the latter, announcement returns are negatively correlated with the spun-off’s relative size. We also examine the effects of a firm’s ownership structure on its choice of spin-off method, focusing on controlling family ownership, affiliated firm ownership, and blockholder ownership. Although we find that blockholder ownership concentration is negatively associated with the likelihood of captive spin-offs, we do not obtain consistent results regarding the other ownership variables. Note, however, that these results should be interpreted with caution because these ownership variables may not fully capture the complex ownership structure of Korean firms. Overall, our results are consistent with the notion that firms may strategically choose the method of their spin-offs to exploit market misvaluation, and such a choice can signal the market regarding their valuations. That is, equity spin-offs can be chosen to allocate undervalued shares to incumbent shareholders, which will attract positive market reactions, whereas captive spin-offs can be used as a means of raising capital using overvalued equities, which will result in less favorable market reactions. Adding to the prevailing view that captive spin-offs are used as a means of minority shareholder expropriation, this study offers another perspective that a firm’s choice between equity and captive spin-offs can be driven by a rational reaction to market misvaluation that is not necessarily disadvantageous to minority shareholders. That is, market reactions to corporate spin-offs in Korea can partly be driven by the signaling effect of firms’ spin-off method choices. Therefore, an assessment of whether a spin-off is detrimental to minority shareholders should consider not only the parent firm’s agency issues but also the market valuations leading up to the firm’s spin-off decision.