The purpose of this study is to describe and explain the Bush Administration's policy toward the Iranian nuclear problem and its change from theoretical perspectives of foreign policy thought and the governmental politics mode. As the result of the analysis, first, there were divisions and conflict over the policy about the Iranian nuclear issue between a coalition of hard-liners in the Vice-President's Office and the Defense Department, on one hand, And their policy position were largely determined by foreign policy thought shared by policy-makers of each coalition. Whereas a policy of confrontation favored by the hard-liners reflected prescriptions offered by neo-conservatism, a policy of limited engagement preferred by the moderates was guided by realism. Second, the policy of passive confrontation was the political resultant of competition and conflict between the hard-liners and the moderate, and reflected the policy position favored by the former who prevailed over the policy-making process. Third, a change of policy to one of limited engagement during the 2nd Administration, resulted mainly from the factor that initiative and control over the policy-making process were shifted to the hands of the State Department moderates. The changed policy of limited engagement was primarily determined by the realist thought shared among them and a compromise in which to reflect the position of the hard-liners.