The aim of this study was to assess how the different aspects of nature of science (NOS) were represented in Finnish and Swedish upper secondary school chemistry textbooks. The dimensions of NOS were analyzed from five popular chemistry textbook series. The study provides a quantitative method for analysis of representations of NOS in chemistry textbooks informed by domain-specific research on the philosophy of chemistry and chemical education. The selection of sections analyzed was based on the four themes of scientific literacy: knowledge of science, investigate nature of science, science as a way of thinking, and interaction of science, technology and society. For the second round of analysis the theme of science as a way of thinking was chosen for a closer inspection. The units of analysis in this theme were analyzed using seven domain specific dimensions of NOS: tentative, empirical, model-based, inferential, technological products, instrumentation, and social and societal dimensions. Based on the inter-rater agreement, the procedure and frameworks of analysis presented in this study was a reliable way of assessing the emphasis given to the domain specific aspects of NOS. All textbooks have little emphasis on the theme science as a way of thinking on a whole. In line with the differences of curricula, Swedish textbooks emphasize the tentative dimension of NOS more than Finnish textbooks. To provide teachers with a sufficiently wide variety of examples to discuss the different dimensions of NOS changes to the national core curricula are needed. Although changing the emphasis of the curricula would be the most obvious way to affect the emphasis of the textbooks, other efforts such as pre- and in-service courses for developing teachers understanding of NOS and pedagogic approaches for NOS instruction to their classroom practice might also be needed.