In order to enable the accelerated preclinical and clinical pharmaceutical development of formulations based on nanomilling, a screening media mill was developed and evaluated for the production of nanoparticulate active pharmaceutical ingredients (API). The screening media mill is based on the principle of a conventional planetary mill, equipped with up to 24 milling beakers of 0.05-1.0 mL individual milling chamber volume. The applicability of the screening media mill was evaluated by 0.7-12.8 mg naproxen (2wt%) per batch with a nanomilling formulation known from the literature. A case study for the preclinical formulation development is presented, applying 42 screening experiments by one operator within 5 working days, using in total 110 mg API. Promising nanomilling formulations with median particle sizes below 200 nm could be identified, suitable for preclinical in vivo studies. A second case study for the early clinical development of another proprietary API showed the successful formulation development within 12 working days. Up-scaling to a miniaturized stirred media mill of 10 mL milling chamber volume resulted in a satisfying comparability of the selected formulations, with varying performance. Further up-scaling of the most promising formulation to a laboratory-scale stirred-media mill showed the successful production of 250 g API with a median particle size of 140 nm.