This paper investigates the development of relative clauses in the speech of one German-speaking child aged 2;0 to 5;0. The earliest relative clauses we found in the data occur in topicalization constructions that are only a little different from simple sentences: they contain a single proposition, express the actor prior to other participants, assert new information and often occur with main-clause word order. In the course of the development, more complex relative constructions emerge, in which the relative clause is embedded in a fully-fledged main clause. We argue that German relative clauses develop in an incremental fashion from simple non-embedded sentences that gradually evolve into complex sentence constructions.