Critical Thinking & Problem Solving belong to 21st century skills that enhance ways of thinking, learning, working and living in the world. When combined with well-designed educational activities, mobile technology has the capacity to foster these abilities. This study evaluates the Critical Thinking & Problem Solving skills of ninth-grade students who participated in mobile-supported labs. According to the findings of a questionnaire provided to students, their skills have improved. Students' written responses to open-ended questions before and after the mobile-supported Labs revealed interesting data about their improvement. Also, records of students' written discussions on the Viber-platform, throughout the process, revealed aspects of critical thinking & Problem Solving development. [For the full proceedings, see ED639391.]