Primary aim of this dissertation is to research, present, critically reconsider and compare with similar theories ecological ethics (ecoethics) by American forester, ecologist and author Aldo Leopold (1887–1948) – based on the concepts of land ethic and ecological conscience – by using primarily subject-matter and methodological features of integrative bioethics as an innovative concept within contemporary bioethical discussions. Research of Leopold’s opus and intellectual influences that shaped his attitudes will be upgraded by considering Leopold’s ecoethical ideas in relation to the work of Van Rensselaer Potter, the American “father of bioethics”, who considered himself as Leopold’s follower, as well as in relation to the development of bioethical theory and bioethical movement, with emphasis on biocentric tendencies that mark the concept of integrative bioethics, as well. In context of exploring the notions of life, nature, human, subjectivity, rationality, consciousness, conscience, freedom and responsibility within Leopold’s work and Leopoldian tradition, as an argumentative support there will be used the existential-phenomenological reflection of Maurice Merleau-Ponty and Thomas Fuchs, the ethical thought of Immanuel Kant and Milan Kangrga, the ecosophical and deep ecological thought of Arne Næss, the social ecological thought of Ivan Cifrić, the philosophy of responsibility of Hans Jonas, and the bioethical thought of Fritz Jahr, a European “father of bioethics” – all of them very important authors regarding Euro-continental tradition of bioethics. Leopold’s ethical imperatives, inscribed into his land ethic, will be problematized especially in relation to Kant’s and Jahr’s ethical imperatives, in order to formulate a biocentrically founded integrative-bioethical imperative (as a fundamental principle of bio/ethics which would response to the challenges of today and future), as well as to contribute accordingly to further expansion and articulation of the orientational field of integrative bioethics. In each of the research thematic units of the dissertation, materials in the form of literature relevant to a particular topic will be used, and in the preparatory part, the collection and/or systematization of the necessary materials will be approached. Reading and interpreting the literature will be approached by critical, analytical and synthetic, as well as the comparative methods, which will examine the viability of the hypotheses and draw conclusions. In general, the research will be based on the methodological assumptions of integrative bioethics (interdisciplinarity, transdisciplinarity, pluriperspectivity, integrativity). Dissertation will be divided into four basic thematic units which will further be divided according to the requirements of the research. The introductory chapter, which precedes these four units, will explain the basic framework and basic (hypo)theses, as well as the context of considering the main topic of the paper. It includes issues of the scientific/technical civilization and the global environmental crisis, as well as the ecoethical/bioethical responses to these challenges. The first unit will consist of research into the life and work of Aldo Leopold, i.e. Leopold’s thought development, with a review of tendencies, authors and schools that influenced his work (Lorbiecki 2016), focusing on the impact of environmental thought of Ralph Waldo Emerson and Henry David Thoreau (Worster 1994) and other American thinkers. Exploring, questioning, and potentially challenging a given claims suggests that the Leopold was writing under the influence of American pragmatism and Darwinist social evolutionism presented by Arthur Twining Hadley (Callicott 2009). This will be followed by a systematic review of the Leopold’s work, with an emphasis on the collection of essays A Sand County Almanac (Leopold 1949) and the concepts of “land ethic” and “ecological conscience” which will be interpreted as a paradigmatic form of biocentric approach to the non-human living beings, the natural environment of humankind and to the nature in general. In the second large part of the paper, the research focus will be shifted to the influence of Leopold’s thought on Van Rensselaer Potter, an American “father of bioethics” (Potter 1971, Potter 1988) and, consequently, the development of the bioethical movement. The biocentric character of Leopold’s ecoethics will be emphasized (as opposed to the anthropocentric model), which was most likely the crucial motive for Potter’s fascination with Leopold. Consideration of the relationship between Leopold and Potter will be extended to the exploration of conceptual similarities between Leopold and the European “father of bioethics”, Fritz Jahr (Rinčić, Muzur 2012). Leopold’s ecoethical imperative (“Right action is anything that contributes to the preservation of stability, integrity and preservation of life, and everything else is wrong”; Leopold 1949) will be related to Jahr’s bioethical imperative (Rinčić, Muzur 2012), but also to Kant’s categorical imperative (Kant 1990), the categorical imperative of Jonas’s ethics of responsibility (Jonas 1990) and the imperatives of Schweitzer’s ethic of reverence for life (Cicovacki 2009), in order to formulate a unifying integrative-bioethical imperative. The third part of the paper will be devoted to the comparison (and articulation of fruitful correlation) of Leopold’s ecoethics and the thoughts of Arne Næss, the founder of “deep ecology” or “ecosophy” (Næss 2002, Næess 2005, Markus 2006), following the previous interpretation of Leopold’s ecoethics as a biocentric conception. The focus will be on the concepts of anthropocentrism and biocentrism, as well as on the concepts of consciousness and conscience, but also on other concepts relevant in this context (life, nature, man, subjectivity, intelligence, freedom, responsibility). Also, it will be inevitable to compare Leopold’s and Næss’s “revolutionary” understanding of these concepts with traditional ethical understandings (Kant 1990, Kangrga 1966, Kangrga 2004). However, the basic research motive of this thematic unit is the juxtaposition of anthropocentrism and biocentrism, primarily in terms of consciousness and intelligence. In that sense, the discussion will also include questions about the relationship between the individual human psyche and the evolutionary ecological balance, i.e. the issues of organic mereological (Potrč 2017) unity of micro- (individual), meso- (social and natural community) and macro-levels (biotic community) of cosmological totality. An attempt will be made to prove that selfishness (as the action of the “disjointed self”) present in the human community extends analogously to human action towards non-human beings of the Earth or nature in general. The fourth and last part of the dissertation will be a summary of previous research, presented with regard to the concept of integrative bioethics, which is characterized by interdisciplinarity, transdisciplinarity, pluriperspectivity and integrativity (Čović 2004, Jurić 2010). The notion of “bioethical sensibility” (Zagorac 2018) will also be introduced to indicate the fact that Leopold’s insights (which can be interpreted as insisting on the development of “bioethical sensibility”) correspond to integrative bioethics and can contribute to the expansion and articulation of the biocentric approach present in integrative bioethics.