This master thesis offers a novel view on business model portfolio management. Through an empirical case study with BMW AG this study extends the predominant resource- based view on business model relationships by a customer value proposition and profit formula dimension. Through analysing secondary data and conducting interviews with senior BMW managers, 17 different business models were identified. Overall these business models have more than 60 relationships on a key processes and resources, customer value proposition and profit formula level. Based on this analysis a new theoretical framework was developed that clusters all relationships into four distinct relationship types (similar, complementary, conflicting and compatible). This clustering allows for mapping the complex relationships within a business model portfolio on a new and more detailed level. Additional statistical testing has provided first evidence that certain types of relation- ships (similar and complementary relationships) increase business model stability and longevity while other types of relationships (conflicting, compatible relationships) have an opposite effect. As a result, this master thesis contributes to academic literature by offer- ing a new, more holistic perspective on business model portfolios while simultaneously enabling managers to improve business model portfolio management.