People’s knowledge about nature, their interest in nature, their nature experiences, and their values and emotions regarding nature are factors that promote people’s positive views on environmental issues and sustainability. Knowing the variation and patterns in teachers’ and student teachers’ views is an essential step in considering the ways in which sustainability might be interpreted and enacted in schools and in teacher education. The aim of this study is to analyze student teachers’ views on the importance of species and species identification in general and as a part of their professional development regarding their understanding of biodiversity and sustainability. A total of 426 student teachers in Finland, Norway, and Sweden answered a questionnaire consisting of fixed and open-ended questions. Mixed methods were used: t test and analysis of variance for quantitative data and inductive and deductive, model-based content analysis for qualitative data. According to the majority of student teachers (85%), both species identification and biodiversity are important for sustainability; species identification in general was important to 58% of them. Their statements about importance contained mostly ecological views (46%), followed by emotional (17%), educational (16%), and utilitarian (11%) views. The remainder of the student teachers’ statements (10%) contained negativistic or indifferent views. The reasons for the low percentage of educational views are discussed. The implications of the results for teacher education worldwide are emphasized, especially the importance of those teaching methods that have the potential to increase student teachers’ understanding of sustainability.