This article presents the findings of an action research study that evaluated the effectiveness of differentiated instruction in the subject of Information and Communications Technology (ICT) in primary education in Greek primary schools. Effective teaching poses a challenge to all educators in all educational levels. The subject of ICT poses multiple challenges to educators due to its applied nature, the limited allocated time and the diverse needs of the students. A differentiated teaching intervention was designed and applied from January to March 2020 to 113 upper elementary students from two elementary schools in Athens. The findings of the research highlight the improvement of the quality of the students' assessment and the level of students' active participation due to differentiated instruction. Furthermore, the strategy of flexible grouping, the technique of "thumb it up" cards and the applied differentiated working routine proved to be highly effective. Lastly, the implementation of asynchronous working combined with hierarchical learning activities proved to be challenging to the educator due to its complexity. Based on these findings, the article discusses the importance of further research in the systematic implementation of differentiated instruction in mixed ability classrooms and in multiple subjects.