Abstrak
Vocabulary mastery constitutes a fundamental component of English language learning, supporting students' ability to comprehend and use the language effectively. However, many junior secondary school students encounter persistent challenges in understanding meaning, recognizing word forms, and applying vocabulary appropriately in context. This study investigates the impact of Video-Based Experiential Learning (VBEL) on vocabulary mastery among Grade VIII students at SMPN 7 Tarakan. The research utilized a pre-experimental one-group pretest-posttest design with 22 students from a single class, selected based on specific research criteria. Data were collected using a validated vocabulary test that assessed three key dimensions: form, meaning, and usage. The results were analyzed through descriptive statistics, paired-samples t-tests, and effect size calculation (Cohen's d). The findings indicate that VBEL significantly enhanced overall vocabulary mastery, as evidenced by an increase in pretest and posttest scores from 23.08 to 28.59 (a gain of 5.50 points), with a Cohen's d of 0.51, representing a medium effect size (p = .026). Nevertheless, the three vocabulary dimensions exhibited uneven developmental patterns: the form dimension demonstrated the greatest improvement, the meaning dimension remained relatively unchanged, and the usage dimension declined. These results offer preliminary insight into VBEL's potential for English as a Foreign Language (EFL) vocabulary learning at the junior secondary level in Indonesia, while also emphasizing that vocabulary development may not progress uniformly across all dimensions during short-term interventions. Due to the limitations of the research design, these findings should be interpreted with caution and not broadly generalized. Future studies are encouraged to employ a quasi-experimental design with a control group, conduct pilot testing of instruments prior to data collection, and extend the intervention duration to enhance the validity of the findings and deepen understanding of VBEL implementation in more diverse learning contexts.