Over the past decade, the financial crisis has led to reduced government funding for academic libraries in Greece. Now more than ever, it is imperative for library managers to improve their knowledge and understanding of cost behavior, in order to effectively deliver high quality services at decreasing costs. To do so, they need to apply clearly-defined costing methods, such as Time-Driven Activity-Based Costing (TDABC), that allow them to identify the various costs involved in the library processes. In our study, we applied the TDABC method at the medium-sized library of the University of Macedonia (UoM), in Thessaloniki, Greece, to evaluate the costs of the Inter-library Loans (ILL) services. Since the library managers did not adopt a cost allocation method, the cost estimation of the UoM ILL services was rather simplistic and rudimentary. Our research provides empirical evidence of the advantages of TDABC in an academic library setting. Namely, the TDABC method can help library administrators decide how to successfully allocate the available resources and improve the efficiency of the library processes.