The paper examines the concept of narrative unreliability across the border of fictional and factual narration, more specifically the possibilities and restrictions of applying this concept to autobiographical texts. Shen and Xu propose three types of unreliability in autobiography: intratextual, extratextual and intertextual. While the intratextual type of unreliability might be close to unreliability in fiction, the intertextual and extratextual types are radically different. In an attempt to synthetize existing approaches (primarily by Nünning, Fludernik, Phelan, and Yacobi), I will show that a crucial aspect of unreliable narration in fiction is the reader's hypothesis of the author's intention to show the narrator as unreliable: the reader shares this effect with (his/her projection of) the author. By contrast, extra- and intertextual unreliability in an autobiographical text that employs "direct telling" is likely to turn the reader against the author as it questions the author's honesty. This fundamental difference casts doubt on the usefulness of the concept of narrative unreliability for autobiography. Furthermore, by blurring the boundary between fiction and autobiography, autofiction and metafictional autobiographies challenge the notions of truth and reliability as applied to autobiographical writing. What could be seen as a signal of narrative unreliability in a work of fiction serves a different purpose in these kinds of texts, as I will demonstrate using the example of Max Frisch's Montauk.