Like larger companies, small and medium-sized enterprises (SMEs) need to develop and implement digitalization strategies. These help to address necessary organizational- and technology-related changes in order to create competitive advantages. However, SMEs often face specific challenges, including a lack of IT know-how, relevant market information and appropriate methods for developing a strategy. In this paper, we present a lightweight, architecture-based method including its underlying model for the development and implementation of digitalization strategies in SMEs. It was developed by following the Action Design Research (ADR) method and in cooperation with two medium-sized companies. Rather than adopting highly abstract and complex enterprise architecture frameworks, we suggest creating easy-to-use visualizations of the enterprise architecture, the business ecosystem and related cross-layer dependencies. While transferring the discipline of enterprise architecture (EA) into the context of digital entrepreneurship, we derived four design principles helping to enrich the theoretical body of knowledge in this research area.