The following essay approaches Nietzsche's presence in Heidegger's Black Notebooks in order to clarify and analyze the particular philosophical role Nietzsche plays in them. Starting with the definition of basic hermeneutical tools for reading and interpreting those hermetic and certainly unique texts in the Heideggerian corpus, Nietzsche's figure emerges not only as a privileged reference center for the Heideggerian thought in the 1930s and 40s, but also and mainly as a fundamental impulse for a profound reformulation of its main coordinates