Sustainability issues have been a popular and important topic on the world’s agenda the recent years, which has caused businesses to follow the policies of operating more sustainable. One of the latest introduced guidelines is the Global Goals imposed by the United Nations to be met by 2030. In light of these goals, awareness regarding sustainability issues among consumers and other stakeholders has increased, leading to that change is inevitable for businesses to start operating sustainably. The concept of sustainable business model innovation therefore becomes relevant. There is a lot of research regarding sustainable business model innovation. However, the research is heavily focusing on theoretical aspects of it, and less is given to the practical creation and implementation of sustainable business models. Further, less focus is given to start-up companies specifically. Due to the identified research gap, this study aims to answer the research question: “How can start-ups successfully create and implement sustainable business models to become an established actor on its specific market?” The purpose of this study is to create an understanding and contribute with extended knowledge of how sustainability is practiced in start-ups. More specifically, how sustainable business models are created and implemented in start-ups. A qualitative abductive approach was used to fulfill this purpose. Additionally, six semi-structured interviews were conducted with founders of start-ups and business coaches from Swedish incubators, which were structured based on the themes from the Lean Start-up Framework (LSF). This framework, along with the Triple Layered Business Model Canvas (TLBMC) showed to be of importance after the theoretical review. The key findings retrieved displayed that the LSF is suitable to describe the sustainable start-up process as well. Yet, the TLBMC needs to be integrated to fulfill the purpose of sustainability. Further, the benefit versus impact is shown to be of great importance whereas the framework’s components were modified in that sense as well in those cases needed. This study theoretically contributes to extended knowledge and additional components of the Lean Start-up framework that are advocated to be crucial to create a sustainable business model. These additional components are further of value for the existing field of research. Practically, by the extended and modified framework, it offers valuable insight for entrepreneurs with a business idea where the purpose is to offer a sustainable value proposition. Lastly, this study contributes to a social level by providing guidelines on the implementation of sustainability in the business model, leading to the encouragement to operate sustainably and towards a better environment and society.