<![CDATA[This study aims to develop and examine the effectiveness of a Mobile Devices-based learning medium integrated with Problem Based Learning (PBL) to improve students' Computational Thinking Skills (CTS) in Informatics learning at SMP Negeri 21 Padang. The development followed the ADDIE model (Analysis, Design, Development, Implementation, and Evaluation). This research used a quantitative approach with a Quasi-Experimental Pretest-Posttest Control Group Design, involving 60 grade IX students (30 in the experimental class and 30 in the control class) selected through cluster random sampling. Data were collected using media and material validation sheets, teacher and student practicality questionnaires, and a Computational Thinking Skills test. The results showed that media expert validation obtained an Aiken's V of 0.886 (88.61%) and material expert validation obtained 0.882 (88.20%), both in the Very Valid category. The practicality test showed 90.00% (teacher) and 93.80% (student) responses, both in the Very Practical category. The Independent Sample t-Test on posttest scores showed tcount = 10.864 > ttable = 2.002 (p < 0.05), indicating a significant difference between the experimental and control classes. The N-Gain score of the experimental class (0.680, moderate category) was higher than that of the control class (0.265, low category). Thus, the Mobile Devices-based learning medium integrated with PBL is valid, practical, and effective in improving students' Computational Thinking Skills in Informatics learning.]]>
