The possibility of any meaningful relationship between the legal realists and natural law looks at first rather far-fetched. When it first appeared on the jurisprudential scene, legal realism was savagely attacked by proponents of natural law theory. To this day legal realism is depicted as a modernist, critical, at times almost nihilist approach to law, the polar opposite of the ancient natural law theory that traces its roots to Greek and Roman philosophy, and insists on unchanging objective values. And yet, two of the most famous legal realists, Karl Llewellyn and Jerome Frank, expressed in some of their writings more than a passing endorsement of natural law theory. The purpose of this essay is to try and explain this seemingly odd aspect of their work and in this way help in reassessing their work. We do so by explaining how they understood natural law and how they incorporated it in their work. Though they did not understand the term in precisely the same way, for both of them natural law was connected to the values of the community, which both of them thought were central to understanding law, for explaining how it could remain relatively certain, and ultimately, how it derived its authority.