The term of 21st century skills has become a key concept in the field of education. It has attracted researchers' attentions and included in some of the cognitive taxonomies used in the fields of curriculum development and educational assessment. In the 21st century, the teaching curriculum and instruction have started to transform in a way consistent with the change of the targeted competences that an educated person should have. This requires classroom assessment applications to change so that they can be in line with the nature of these competences and support their development. This study discusses the skills that have gained importance in the 21st century education (21st century skills), the interaction between these skills and the classroom assessment, and the transformation of assessment activities to cover these skills. The study also includes one sample assessment activity and rubrics that are developed by the researchers in order to guide teachers how to include these skills in their daily teaching plan and how to assess them.