This article represents the first attempt to formulate a hypothetical sequence for German case acquisition by Dutch-speaking learners on the basis of Processability Theory (PT). It will be argued that case forms emerge corresponding to a development from lexical over phrasal to interphrasal morphemes. This development, however, is subject to a correction factor due to the principle of direct mapping. In addition, the unmarked alignment hypothesis allows for a differentiation between similar case contexts (e.g., preverbal and postverbal nominative or accusative arguments). A cross-sectional study was performed in order to examine whether the German case system is indeed acquired according to the hypotheses derived from PT. “Fill-in-the-blanks-exercises” were analyzed from 704 Flemish second-language learners of German. The results of the study do indeed suggest a development in line with PT.