Introduction Ecocriticism in literature concentrates on literature and the environment or the Nature; it means it focuses on literature and the physical environment. Such study calls for collaboration between natural scientists, writers, literary critics, anthropologists, historians, and other disciplines. Poets and authors have always been under the influences of the world around and the environment so that nature changed to be a source of inspiration to them. Background Studies Ecocriticism and Environmental literary studies were first introduced to the world of literature in 1970 in world’ s most important assembly “ The Western Literature Association” (WLA). After the Industrial revolution, human being transformed his connection with nature and started to experience a new season in his life. The earlier connection was based on a mutual relationship, but the new one was entirely shifted to something far from a mutual link. In other words, after the Industrial revolution, human being occupied an upper position and nature suffered from a banal one. Incidentally, the ecocritics enjoy various methods of analysis in their studies; some believe that nature is not more than a humanized structure which some poets like William Wordsworth started to form in their works. Many of these critics put nature as a counterpart of culture, or identify nature as instinct. Instinct is the main inner motive which transfers its effects to other creatures. It is identified with nature or the animal’ s desire to do profitable deeds. Materials and Methods The present study attempts to reveal ecocritical works and thoughts of two most significant Persian and American poets/authors, Nimā Yushij (1897-1960) and Ralph Waldo Emerson (1803-1882). To do this, the poetry and the letters of Nimā together with Emerson’ s book titled Nature (1836) have been selected. It is indicated how Nimā and Emerson’ s idealism is closely related to nature, and how it is based on Human-God-Nature-Justice circle. It is shown that nature is the major source of this circle. Hence, the present study, by the use of American School of Comparative studies, while applying a library-analytical approach, tries to compare and contrast the major thoughts of Nimā Yushij and Ralph Waldo Emerson due to their literary environmental writings. Furthermore, it is emphasized that these two poets belong to different languages and literatures; however, as far as the American School is based on Eclecticism in comparative studies, it is hoped that the major nature-oriented themes and ideas of these poets might be revealed in this essay. It should be also considered that the American School of comparative studies does not concentrate only on the effects or influences in literary studies; to such school, literary movements, genres and literary types, and the topics and themes of world literature are the fundamental spots of studies. Results and Discussions The study discloses how Emerson’ s outlook to nature is more philosophical than Nimā ’ s. When he talks about nature his idealistic motives start to appear. Both poets insist on the unity of human being and nature by unifying human history and natural history. The beauty of nature is another major theme of their poetry; both look at nature as the source of beauty and its pleasures. Emerson believes that the ultimate end of the cosmos is a desire to the beauty. Why human being is so much interested in the beauty is beyond the thoughts and logics of man. Furthermore, Nimā ’ s ecocritical tendencies are closely related to coexistence of man and nature, and the poet’ s thoughts are not separated from the beauties of nature and its inspiration. Nature, environment, and the world around are at the core of both Nimā and Emerson’ s thoughts and writings. To live naturally and to get involved with nature are their ideal way of life. To them, solitude and primitivism are man’ s solution to release him/her from the chains of society. Both of them complain about human being’ s distance from nature; they believe that solitude is mankind’ s opportunity to conform his/her soul to nature.