This study aimed to investigate eighth-grade students’ mathematical communication competency and mathematical literacy performance in a classroom experiment designed based on the mathematical modeling approach. Accordingly, a teaching experiment methodology was applied. Data were collected from three eighth-grade students through the Mathematical Communication Competency Measurement Tools, video recordings of the teaching episodes, student products, and clinical interviews before and after the teaching experiment. PISA mathematics proficiency level and communication competency level assessment schemes were used in the data analysis process. A deductive analysis was performed on the data collected through the clinical interviews, whereas a retrospective analysis was conducted to examine the data collected through teaching episodes. The results showed that the modeling-based teaching experiment helped develop the mathematical communication competency of all participating students. The results also showed that improving students’ mathematical communication competencies increased their mathematical literacy performances.