This study reports a small part of a large-scale study. In this vein, trends in cognitive demand levels of mathematical tasks in the Algebra Learning Domain of 5 mathematics textbooks prepared according to four middle school mathematics curricula that have been updated since the beginning of the 2000s in Turkey were determined. This study is a document review, and the criterion sampling method was used to select textbooks. The cognitive demand levels of the mathematical tasks in the examined books were analysed according to the content analysis. The study revealed that the tasks in the middle school mathematics textbooks written according to the updated mathematics curriculum in Turkey in the 2000s are generally low cognitive demand tasks. Also, some suggestions are made for further research according to the findings.