Advance care planning is a voluntary process whereby individual preferences, values and beliefs are used to aid a person in planning for end-of-life care. Currently, there is no local instrument to assess an individual’s awareness and attitude towards advance care planning. This study aimed to develop an Advance Care Planning Questionnaire and to determine its validity and reliability among older people in Malaysia. The Advance Care Planning Questionnaire was developed based on literature review. Face and content validity was verified by (...) an expert panel, and piloted among 15 participants. Our study was conducted from October 2013 to February 2014, at an urban primary care clinic in Malaysia. Included were those aged >50 years, who could understand English. A retest was conducted 2 weeks after the first administration. Participants from the pilot study did not encounter any problems in answering the Advance Care Planning Questionnaire. Hence, no further modifications were made. Flesch reading ease was 71. The final version of the Advance Care Planning Questionnaire consists of 66 items: 30 items were measured on a nominal scale, whilst 36 items were measured on a Likert-like scale; of which we were only able to validate 22 items, as the remaining 14 items were descriptive in nature. A total of 245 eligible participants were approached; of which 230 agreed to participate. Factor analysis on the 22 items measured on a Likert-scale revealed four domains: “feelings regarding advance care planning”, “justifications for advance care planning”, “justifications for not having advance care planning: fate and religion”, and “justifications for not having advance care planning: avoid thinking about death”. The Cronbach’s alpha values for items each domain ranged from 0.637–0.915. In test-retest, kappa values ranged from 0.738–0.947. The final Advance Care Planning Questionnaire consisted of 63 items and 4 domains. It was found to be a valid and reliable instrument to assess the awareness and attitude of older people in Malaysia towards advance care planning. (shrink)