Many Swedish schools collaborate with schools in other countries. This research study focuses teachers’ experiences of transnational school collaboration between Swedish schools and schools in other countries. The aim of the study is to investigate the outcome of such projects and find explanations why teachers make a choice to use international school twinning as a part of their teaching in environmental education. The study concentrates on teachers’ motives for involving their students in transnational school exchange regarding environmental issues. A part of the investigation is also to elucidate how teachers conceive cultural meeting and cooperation that occurs in the context of transnational school exchange projects. The conditions for carrying on such projects are also investigated. The study uses semi-structured interviews with upper secondary school teachers from Sweden and Britain. Most interviews were performed at the respective teachers’ schools. The processing of the interviews consists of transcribing followed by a narrative report and analysis. The investigation shows that the teachers find that their students’ personal development is highly improved by international school exchange both through experiencing a different culture and cooperating with young people from another country. The teachers also believe that their students’ environmental awareness is improved by experiencing investigations and collaboration in another part of the world. The positive effects from the exchange projects are also considered as mutual for the students in both of the cooperating countries.