The research problem was analyzed from the perspective of neoclassical realism, which is a theoretical framework that assumes a relative distribution of power in an international system as an independent variable that influences state’s foreign policy over time, but which, at the same time, believes that the independent variable alone is not sufficient to explain the concrete foreign policy as a dependent variable. How exactly a particular foreign policy will look like, especially in the short and medium term, will largely depend on intervening variables through which systemic pressures and signals are translated to the unit level. In line with the determinants of neoclassical realism, we analyzed the independent (relative distribution of power in the international system), intervening (American conservatism) and dependent (foreign policy under President Trump) variables, while testing the main hypothesis according to which American conservatism is the intervening variable that influenced the formulation of President Trump’s foreign policy.In the first step, we analyzed the independent variable, i.e. the relative distribution of power in the international system and the U.S. position within the system. The independent variable primarily determines the context and sets the general framework for American foreign policy and was interpreted by using a meta-analysis of indicators of the relative distribution of power in the international system. This analysis allowed us to draw conclusions about the U.S. position and the relative distribution of power in the international system, which are systemic factors that have a general influence on foreign policy formulation. The intervening variable that we assumed influenced the formulation of President Trump’s foreign policy, i.e. American conservatism, was analyzed in the second step. Through the literature review, we analyzed the historical development and characteristics of American conservatism and especially its main variants that were preliminarily identified as variants with the greatest potential impact on the formulation of President Trump’s foreign policy - neoconservatism and paleoconservatism. The analysis of the intervening variable made it possible to identify key elements of American conservatism and its main variants. In the third step, the analysis of President Trump’s foreign policy, as the dependent variable, included the analysis of the main ideas and elements of his foreign policy in the period 2017-2021, by applying qualitative data analysis, i.e. method of (reflective) thematic analysis with the use of NVivo software. The thematic analysis was conducted on a sample of documents taken from the archives of the University of Santa Barbara The American Presidency Project and allowed us to identify and interpret basic ideas and elements of the U.S. foreign policy under President Trump, as well as to identify traces of American conservatism in those ideas and elements. The complete analysis of the independent, intervening and dependent variables allowed us to draw conclusions about the impact of American conservatism, as the intervening variable, on the formulation of President Trump’s foreign policy. This analysis led us to the conclusion that numerous elements of American conservatism were present in President Trump’s foreign policy, especially the variants that were put on the sidelines of the American conservative movement after WW2. Trump’s foreign policy showed a significant level of coherence and consistency, leading us to draw conclusions about the existence of Trump’s doctrine. The significant presence of traces of American conservatism in President Trump’s foreign policy, along with the analysis of the relative distribution of power and the U.S. position in the international system, confirmed the main hypothesis according to which American conservatism was the intervening variable that influenced the formulation of President Trump’s foreign policy.