Inadequate English vocabulary knowledge hampers English-medium university students’ comprehension of lecture and reference materials. Thus, the researchers aimed to specifically develop an intervention for vocabulary knowledge enhancement, which is a theme-based contentbased instruction vocabulary module for first-semester Diploma in Tourism Management students using the ASSURE model. The rationale behind the vocabulary module development is that students tend to acquire vocabulary faster when they learn it through a familiar and meaningful context. Upon completion of the module’s development, it was examined for validity and reliability. Content validation of the module was evaluated by four experts using the Content Validity Index and Percentage Calculation Method. Meanwhile, the module’s reliability was tested in a pilot study using Cronbach’s alpha test on reliability questionnaire results and paired sample t-test comparison of pre and post-test scores of students’ vocabulary knowledge. The pilot study involved 20 students with varied English language proficiency levels at an English-medium university in Malaysia. Findings of content validation by four experts and module validation by the pilot study indicate that not only does the module have high validity and good reliability, but also succeeds in increasing the students’ post-test vocabulary knowledge scores compared to their pre-test scores. Overall, this study contributes empirical evidence for English as a Second Language (ESL) vocabulary module development. It also proves that a valid and reliable module must be developed by referring to an instructional design model, reviewed by subject matter experts, and tested with the target audience through a pilot study