The thesis focuses on the integration of sustainability in the early stages of startups by developing a new framework. Given the resource constraints and focus on viability, it might be difficult for startups to consider sustainability at these early stages. A literature review revealed a lack of information on this subject. The research investigates the sustainability-related challenges startups face, identifies factors for sustainable business models using expert interviews and literature review. Due to the lack of information related to sustainable early stages start-ups, the author analyses basic principles related to start-ups and sustainability. The author looks into holistic approach to sustainability since a fragmental approach to sustainability risks harming the ecosystem while improving some metrics without systemic overview. Life-centred design is an emerging design approach that focuses on the well-being of all life forms and the health of our planet, thus making a shift from just human-centred design. The life-centred design was taken into consideration since it covers different aspects of sustainability as well as ethics and provides practical guidance for the designing process. Based on literature review and expert interviews the framework was formulated. The developed solution was tested with three early-stage startups, providing practical insights. The author analyses the findings and concludes that start-ups which have sustainability as a core value proposition are already sustainable and their sustainable impacts potentially scales with their product growth. At the same time for these types of start-ups it’s vital to consider additional value for the customer apart from sustainable value. For the start-ups with core value not directly related to sustainability, the sustainability can be embedded within a lean approach and aligning sustainability with their business goals if it doesn't require sacrificing limited resources such as money. Finally, the author suggests tools that raise awareness of participants and can be useful for holistic picture, based on findings during the workshop.