The transtheoretical model (TTM) has been used as one of the major constructs in developing effective cognitive behavioural interventions for smoking cessation and relapse prevention, in Western societies. This study aimed to examine the reliability and construct validity of the translated Bahasa Malaysia version of TTM questionnaire among adult smokers in Klang Valley, Malaysia. The sample consisted of 40 smokers from four different worksites in Klang Valley. A 26-item TTM questionnaire was administered, and a similar set one week later. The questionnaire consisted of three measures; decisional balance, temptations and impact of smoking. Construct validity was measured by factor analysis and the reliability by Cronbach' s alpha (internal consistency) and test-retest correlation. Results revealed that Cronbach' s alpha coefficients for the items were: decisional balance (0.84; 0.74) and temptations (0.89; 0.54; 0.85). The values for test retest correlation were all above 0.4. In addition, factor analysis suggested two meaningful common factors for decisional balance and three for temptations. This is consistent with the original construct of the TTM questionnaire. Overall results demonstrated that construct validity and reliability were acceptable for all items. In conclusion, the Bahasa Malaysia version of TTM questionnaire is a reliable and valid tool in ass.