This study concerns how technology teachers conceptualize systems thinking and how textbook descriptions of systems can be related to systems thinking. The analysis is conducted using the ‘Freiburg heuristic model of systems thinking’, which uses four dimensions of systems thinking: (1) declarative and conceptual knowledge, (2) modelling systems, (3) solving problems using system models, and (4) evaluation of system models. It concerns both propositional knowledge and problem-solving skills, which makes it suitable for technology education purposes. Four Swedish technology textbooks, intended for years 7–9 in compulsory school (pupils aged 13–16 years), were analysed. The declarative dimension was present in varying degrees through use of terms and concepts related to systems (component, input, output, etc.). System modelling processes, model use, and model evaluation are absent. An interview with three technology teachers working in compulsory school (pupils aged 7–16 years) rendered similar results. When prompted to describe systems thinking and how it is taught, they talked mainly in conceptual terms (e.g., systems as sets of interacting components). To some extent they discussed pupils’ modelling activities, but not how models could be used for problem solving, explanation, or prediction. The teachers also put forward historical perspectives on infrastructure as part of systems thinking. The study suggests that systems thinking in compulsory school could be developed further. The use of system models to understand for example complex environmental problems related to technology use, or perform life cycle analyses is not emphasized, neither by the teachers nor in the textbooks.