This pre-experimental study investigates the efficacy of the Busuu application in enhancing vocabulary mastery and explores student experiences during vocabulary learning. Utilizing a quantitative approach, pre-test and post-test data were collected from 30 underperforming eleventh-grade Business and Marketing students at SMK Negeri 1 Banda Aceh. The results reveal a significant improvement, with the average pre-test score of 6.8 rising to 9.9 in the post-test. Additionally, student satisfaction was assessed through a questionnaire, indicating positive feedback. This research serves as a foundational exploration of the Busuu application's potential impact on vocabulary acquisition, encouraging further in-depth investigations by future researchers.