Graduates expect higher education to provide both subject-specific knowledge as well as cross-curricular competencies in order to handle new and unknown situations in their professional life. In this regard, it is problematic that the latter construct is still both theoretically and empirically vague. In addition, concerning the fostering of cross-curricular competencies, higher education often neglects the interplay of cognitive, metacognitive and motivational skills. This article will address these shortcomings. Based on an empirical study with German university students analyzing cross-curricular problem-solving competencies, a diagnostic model for measuring these competencies will be outlined. Subsequently, the article will present results that show connections between cross-curricular problem solving and motivational and metacognitive skills, notably self-efficacy and epistemological beliefs. These results show that cross-curricular problem-solving competencies depend on how much students regard knowledge as flexible and modifiable. In addition, it could be observed that self-efficacy seems to assume a relevant role. Once more, the results underline the importance of the promotion of epistemological beliefs, in particular critical thinking and reflexivity, as well as encouraging students to experience their own competence.