In last 50 years, Belgium has evolved from a central to a federal state. While this process was driven by the Flemish and Francophone communities (and influenced by the Brussels-Capital Region), a fourth much smaller entity known today as ‘German-speaking Community’ was also integrated into the federal arrangement. This article reviews the latter’s political history to go beyond the common explanation that its statute was a consequence of the Belgian federalization dynamic. By using historical scholarship and testimonial interviews, it shows that neither the demand nor conferral of autonomy were automatic and that regionalist party pressures on the regional level and intra-party multi-level negotiations were equally necessary for the communities’ recognition as federal entity. With lessons from what it presents as a least likely case of federal entities whose autonomy dynamics followed that of larger communities with strong regionalist pressures, the article develops the concept of ‘federalization in the slipstream’.