As the world is waking up to the reality of the climate change, environmental issues are becoming more and more important and demanded both by businesses as well as customers. Tourism has a great responsibility in global development towards sustainability as it directly affects the environment and local communities, both socially and economically. The core of sustainable development is in understanding the value of the environment and its resources and choosing to preserve them. Sustainability covers the environmental, social and economic dimension which all go hand in hand in the tourism industry. All tourism businesses should have a positive triple bottom line where nature is not exploited, people are valued, and profit is guaranteed. The purpose of this thesis is to help a small accommodation business in Costa Rica to act in a more sustainable way in their everyday practices. We created a sustainability plan for The Lion Fish Hostel with practical guidance based on different theories, industry guidelines, previous researchers and the interviews we conducted with local professionals. The sustainability plan helps the business to identify its key issues and impacts on the environment, gives recommendations on how to change the business policies into more sustainable direction and focuses on giving practical advice on the daily procedures. It also introduces the educational aspects of sustainable management as well as local partnership possibilities. Our research-oriented thesis is a qualitative research which mainly consists of field observations and interviews conducted in Puerto Viejo, Costa Rica. From these interviews, we gathered a good amount of insights on local environmental issues, practices for sustainable development and knowledge about the need and demand for environmental management. According to the interviews, observations and previous research, the most important aspects regarding environmental management are water and energy management, waste treatment, environmental education and social engagement. The created sustainability plan can work as a guidance also for other small accommodation businesses around the world. Practical examples that The Lion Fish Hostel could do to act more responsibly, according to the created sustainability plan, are for example recycling, informing guests about saving water and avoiding plastic, organising events such as Beach Clean for both staff and guests, as well as investing in energy-efficient equipment and eco-friendly cleaning products.