Prior studies on the determinants of budgetary slack have not produced consistent results because most of them identified the causes of budgetary slack based on the assumption of human opportunistic individualism and failed to accurately construct the causal relationships among variables. The purpose of this study is to supplement these studies showing inconsistent conclusions by examining budgetary slack from the perspectives of individual ethics and commitment, setting ethical judgment orientation as the variable for ethical behavior and organizational commitment as the variable for individual commitment as explanatory variables, and then investigating the effects of these variables on budgetary slack. The research results showed that ethical judgment orientation and organizational commitment moderated the relationship between participative budgeting and budgetary slack. Additional tests for mediating effects conducted to establish accurate causal relationships confirmed that these variables had no mediating effects. The results of this study demonstrated that variables from the perspectives of individual ethics and psychology, namely ethical judgment orientation and organizational commitment, can supplement the existing explanatory variables based on the assumption of individualism to help consistently explain the relationship between participative budgeting and budgetary slack. Furthermore, the research finding that individual characteristic variables such as personal ethics and psychology serve as moderating variables indicates that individual and cultural factors are important subjects of control in building management control systems.