There is substantial evidence that students in higher education who have sophisticated resource-management skills are more successful in their studies. Nevertheless, research shows that students are often not adequately prepared to use resource-management strategies effectively. It is thus crucial to screen and identify students who are at risk of poor resource management (and consequently, reduced academic achievement) to provide them with appropriate support. For this purpose, we extend the validation of a situational-judgment-based instrument called Resource-Management Inventory (ReMI), which assesses resource-management competency (including knowledge of resource-management strategies and the self-reported ability to use this knowledge in learning situations). We evaluated the ReMI regarding factor structure, measurement invariance, and its impact on academic achievement in different study domains in a sample of German first-year students (N = 380). The results confirm the five-factor structure that has been found in a previous study and indicate strong measurement invariance. Furthermore, taking cognitive covariates into account, the results confirm that the ReMI can predict students' grades incrementally. Finally, a multi-group analysis shows that the findings can be generalized across different study domains. Overall, we provide evidence for a valid and efficient instrument for the assessment of resource-management competency in higher education.