<![CDATA[Communication skills are among the essential competencies required in 21st-century learning and play a crucial role in science education. However, students often experience difficulties in expressing ideas, presenting arguments, and communicating scientific concepts effectively. This study aimed to investigate the effectiveness of Problem-Based Learning (PBL) supported by PhET virtual laboratory simulations in improving students’ communication skills on the topic of temperature and heat. The study employed a quantitative approach using a one-group pretest–posttest quasi-experimental design. The participants were 36 eleventh-grade students from a public senior high school in Sorong City, Indonesia. Data were collected through communication skill tests, observation sheets, expert validation instruments, and student response questionnaires. The data were analysed using the Wilcoxon Signed-Rank Test and N-Gain analysis. The results showed a significant improvement in students’ communication skills after the implementation of PBL supported by PhET simulations (Z = −5.244, p < 0.001). The average communication skill score increased from 50.7 on the pretest to 85.5 on the posttest. The N-Gain value of 0.71 indicated a high level of improvement. The greatest improvement was observed in students’ ability to explain observation results using physics concepts, while nonverbal communication showed the smallest increase. Student responses toward the learning approach were predominantly positive, particularly regarding the visualization of temperature and heat phenomena and support for scientific communication. These findings suggest that integrating Problem-Based Learning with PhET virtual laboratory simulations is an effective instructional strategy for enhancing students’ communication skills in physics learning.]]>
