The article explores how the Icelandic public school curriculum for early childhood, compulsory and upper secondary school deals with education for sustainable development. As the curriculum does not often mention the term sustainability, a key with which to investigate signs of education for sustainable development in the three curricula was created. The key encourages a holistic view of sustainable development, where economic, environmental and social factors are not treated as separate entities. It was designed to reflect the goals of the United Nations Decade of Education for Sustainable Development (2005-2014) with research on environmental education and education for sustainable development in mind. The key has seven characteristics: values, opinions and emotions about nature and environment; knowledge contributing to a sensible use of nature; welfare and public health; democracy, participation, and action competence; equality and multicultural issues; global awareness; and finally, economic development and future prospects. Using the key, a variety of signs and indicators that provide a space for teachers and schools to deal with issues of sustainable development were identified. (Contains 7 notes.)