While text and image independently convey meaning, their combination in contemporary texts generates and communicates meaning in novel ways, forming what can be termed a "meta-language." One of the most important educational media is textbooks. Given that geography is widely regarded as a key subject in many educational systems around the world, effective instruction in this field is of particular importance. In light of this, the present study seeks to address the following questions: What methods of text-image interaction are employed to convey meaning in upper secondary school geography textbooks? And to what extent do the images in these textbooks reflect the ideational metafunctions presented in the text?This study adopts a descriptive-analytical approach based on Systemic Functional Linguistics and employs the analytical framework proposed by Unsworth (2006a). Using a simple random sampling method, it analyzes the images found in upper secondary geography textbooks published for the academic year 2019–2020 (1398–1399 in the Iranian calendar). The findings reveal that text and image interact in various ways as outlined in Unsworth's framework. Furthermore, the results indicate that approximately 95% of the images in these textbooks successfully represent the ideational metafunctions of the accompanying texts. However, the study also finds that Unsworth's framework is somewhat incomplete—particularly in the "complementary" and "causal" subcategories—suggesting the need for a revision of its classification system. Finally, it is recommended that Unsworth’s framework be employed in the development of geography textbooks to enhance multimodal communication.