This essay critically engages ontological, rhetorical, ethical, and political themes pertinent to the concept of "sympathy" as it appears in the poetry and prose of Walt Whitman and Jane Bennett’s writing on him. I suggest that antagonism is immanent in the "ecology of sympathies" that Bennett theorizes, and that this partly explains why one frequently finds antagonistic articulations deeply intertwined with Whitman’s most sympathetic expressions. I propose that we use the paradoxical—even oxymoronic sounding—trope antagonistic sympathy to evoke this immanent relationship between affiliative and antagonistic flows, energies, and conditions for ethical and political cultivation. The concept of antagonistic sympathy helps us better understand Whitman, the ethical and political qualities, pulls, and implications of sympathy, and it enables us to theorize entanglements of sympathy and antagonism in ways that avoid the worst tendencies of each when isolated from the other. Antagonistic sympathy, I argue, is indispensable for radical democratic and ecological transformation in a time of rapidly intensifying planetary ecological catastrophe.