This paper focuses on system concept use in teaching either chemical core concepts or interdisciplinary chemistry-related topics. The system concept is important in order to develop global competences, and chemistry teaching plays a key role in this context. A questionnaire has been administered to two different samples, Italian teachers and International Baccalaureate (IB) teachers, in order to investigate their opinions about the issues involved. The most significant differences and similarities emerging from the survey have been analyzed mostly by dendrograms and then commented on. With due caution, it is possible to suppose similar attitudes in the two groups of teachers except for some aspects. For example, the analysis of system concept knowledge within pure chemistry highlights some deficiencies: Italian teachers in particular show a low level of epistemological awareness about the systemic character of chemistry, whereas its knowledge would allow not only a chemistry teaching improvement but also a productive use of chemical explanations in other scientific and nonscientific fields, especially in the social sciences; as a consequence, it would facilitate interdisciplinary teaching. Therefore, science teachers need epistemological insight into chemical systemic aspects, that may be provided by high quality textbooks and training initiatives focusing on the systemic character of chemistry and its interdisciplinary connections. In an analysis of chemistry teachers only, Italian teachers support interdisciplinary teaching more strongly than IB teachers, despite the rigidity and the state of crisis of the Italian education system, often attributed to a lack of broad-minded teachers. This evidence indicates a promising resource for the Italian education system. Moreover, a similar kind of questionnaire can be utilized by other education researchers in order to isolate and analyze some teachers' attitudes regardless the very different education systems in which every sample works.