<p>This study aimed to explore the psychological factors related to stock addiction tendencies among Korean adults with stock investment experience and develop predictive models using psychological variables, demographic profiles, and related characteristics. The participants comprised 400 Korean adults aged 19–68 years. The predictive models were validated using regression and decision-tree analyses. The results indicated that neuroticism, extraversion, agreeableness, the behavioral activation system (BAS), impulsiveness, sensation-seeking, risk-taking, and irrational beliefs in stock investment were positively correlated with stock addiction. To address potential heteroscedasticity identified in residuals from the stepwise regression model, a robust regression analysis using Huber’s M-estimator was conducted based on the predictors selected through stepwise regression. The robust regression analysis revealed that overconfident or illogical reasoning, impulsiveness, and risk-taking were key predictors of stock addiction, with drive also showing a significant effect and BIS demonstrating a marginal effect. These five variables together accounted for a substantial proportion of variance in stock addiction while addressing potential heteroscedasticity. The decision-tree model identified risk-taking, stock balance, overconfident or illogical reasoning, reward responsiveness, impulsiveness, extraversion, and minor investor status (defined by low trading volume rather than investment experience) as predictors of stock addiction among Korean adults. These findings highlight that psychological variables<i>—</i>such as overconfident or illogical reasoning and risk-taking<i>—</i>are crucial factors in the development of stock addiction among Korean adults.</p>