Introduction: The Theory of Planned Behavior (TPB) construct is recommended by the World Health Organization to assess intention for vaccination; however, there is yet a validated instrument in the context of booster dose Covid-19 vaccination in Malaysia. The purpose of the present study is to translate and investigate the factorial validity and internal reliability of the TPB construct for booster dose Covid-19 vaccination (TPB-BDV) questionnaire in Malaysia. Materials and methods: In the pre-testing of the study, five experts and 40 Malaysian adults respectively rated the content and validity index of all 11 items of the translated questionnaire in Malay version. Next, 160 Malaysian adults completed the Malay version of Theory of Planned Behavior- Booster Dose Vaccination (TPB-BDV) questionnaire via online. Results: In the pre-testing phase, Content Validity and Face Validity Index for 10 items in Malay version of TPB-BDV achieved cutoff mean score >3.0 for relevancy, clarity, ambiguity, and simplicity. Meanwhile, Item 8 scored low on relevancy. In the main study, exploratory factor analysis suggested three factors consisting of a final 10 items (without Item 8) which accounted for 74.0% of the total variance. The three factors were Attitude (5 items), Subjective Norms (3 items), and Perceived Behavioral Control (2 items). The internal reliability ranged from a = 0.83 to a = 0.93, with an overall value of a = 0.90. Conclusion: The findings suggest that the 10-items Malay version of TPB-BDV is valid and reliable to measure the individual decision in taking the Covid-19 booster-dose vaccine among Malaysian adult population.