Can phenomenologists allow for the existence of unobservable entities such as atoms, electrons, and quarks? Can we justifiably believe in the existence of entities that are in principle unobservable? This paper addresses the relationship between Husserlian transcendental phenomenology and scientific realism. More precisely, the focus is on the question of whether there are basic epistemological principles phenomenologists are committed to that have anti-realist consequences with respect to unobservable entities. This question is relevant since Husserl’s basic epistemological principles, such as the “principle of all principles,” seem to suggest that epistemic justification is limited to what can be originally given in the sense that if an object cannot be given in an originary presentive intuition, then one cannot be justified in believing that this object exists. It is the main aim of this paper to show (i) that interpretative reasons exist for not reading Husserl in such a way and (ii) that systematic reasons exist as to why phenomenologists should not subscribe to this criterion. I shall put forward a different criterion of justification that satisfies the spirit of Husserlian transcendental phenomenology and allows for justifiably believing in the existence of unobservable scientific entities.