This study examines the relationship between the genre of ekphrastic poetry and art ideology. It provides a theoretical argumentation on this innate association in continuation with James W. Heffernan’s observations in the field. The study argues that ekphrasis is theoretically related to the practice of art criticism, which, in its turn, stands on art ideological grounds. Two hypotheses about the nature of the relationship that combines ekphrasis and art ideology are generated from this theoretical investigation. The first is that art ideology is a sine qua non to ekphrasis, and the second is that art ideology especially contributes to the thematic structure of ekphrasis. The validity of this proposition is tested through analyzing Marianne Moore’s poem “The Camperdown Elm,” in which Moore’s own art ideology as explicated in her non-poetic works is utilized. As a result, this study aims to contribute to both the theoretical and analytical studies of ekphrasis genre.