Upper secondary school students today face challenges in interpreting and under-standing the complex world around them. The subject of Religious education and particularly textbooks can be used to give students the tools and knowledge they need. An important development to attain knowledge about is secularization and its impact on the religious landscape in Sweden. Secularization is a complex phe-nomenon and theorizations of secularization today faces challenges to describe the width of developments and changes of religion. I therefore aim to examine text-books in RE to get a deeper knowledge about how textbooks depict secularization and the process of secularization. I also aim to contribute to the didactic knowledge and tools related to the teaching of secularization to students. The method used is a qualitative data analysis of four textbooks used in RE. The theo-retical perspective used is sociologist Inger Furseths ”Religious complexity frame of reference” and the tools that the framework provided. The study showed that textbooks depict linear perspectives of the process of secularization. The text-books do not describe the reciprocal development by religion in relation to secu-larization to any greater extent. The textbooks depict secularization by referring to and describing secularization on different analytical levels.