Current economic, environmental, and social developments indicate that business models solely directed toward continuous economic growth do not suffice to sustain competitiveness in the market anymore. Therefore, business model innovation for sustainability (BMIfS) emerged. It aims to mitigate the generated negative environmental impacts and strives for economic, environmental, and social sustainability. Yet, BMIfS has different motivators. In highly regulated industries, BMIfS is mainly initiated due to new regulations or other external influences. The Swiss railway industry is highly regulated and hence also challenged by the task of balancing executable sustainability initiatives with developing innovative business models for sustainability while sustaining their competitiveness in the market. This thesis aims to analyze how leveraging outbound open innovation can support Swiss railway firms in their BMIfS activities. It investigates the prerequisites and challenges for embedding outbound open innovation into current BMIfS practices to balance sustainability initiatives while ensuring competitiveness. To find out how Swiss railway firms currently execute BMIfS, and which factors influence the engagement in outbound open innovation, semi-structured interviews with four railway innovation experts were conducted and accordingly analyzed.