English is a second language taught in all Malaysian schools. It requires a broad of vocabulary among students in acquiring the second language. However, the lack of vocabulary among students leads to obstacles in language acquisition. This made the students left behind the outperform students in listening, speaking, reading and writing. In order to develop vocabulary among students, project-based learning as social strategy is seen as a medium that could assist students in acquiring the language. The aim of this paper is to investigate how project-based learning could benefit the students in the acquisition of English vocabulary in ESL lessons. 30 students of age 10 had been selected from a school in Pahang, Malaysia to see their performance in enhancing vocabulary through a survey using questionnaire. The post-survey result showed improvement in students’ vocabulary and project-based learning as social strategy demonstrated students’ achievement in enhancing students’ vocabulary. In conclusion, this finding evidently gives a different approach in conducting the teaching and learning during ESL lessons.