This study examines the effectiveness of the Tamil-English Bilingual Method on vocabulary acquisition among Tamil- medium higher secondary school students in Tamil Nadu. Vocabulary development is a critical component of second language learning, particularly in contexts where exposure to English outside the classroom is limited. A quasi- experimental design was employed, with two groups of students (N = 30 each) selected from comparable schools. The control group received instruction through conventional English-only methods, while the experimental group was taught using the Tamil–English Bilingual Method, which strategically employed Tamil as a scaffold to introduce and reinforce English vocabulary. Pre-test and post-test scores were analyzed to measure vocabulary gains. The results revealed a significant difference between the groups. While the control group showed minimal improvement, the experimental group displayed a statistically significant increase in vocabulary acquisition. The bilingual approach not only enhanced comprehension and retention but also increased learner confidence in using new vocabulary. The findings suggest that bilingual instruction provides meaningful contextual support, allowing students to connect prior knowledge in their mother tongue with new linguistic input in English. This method holds particular promise for rural and low-English- exposure contexts in Tamil Nadu, where students face challenges in developing adequate English proficiency. By integrating the mother tongue in vocabulary instruction, teachers can create a more inclusive and effective learning environment. The study highlights the potential of bilingual pedagogy as a practical and culturally responsive strategy to strengthen English language education in similar multilingual contexts.