Introduction: This study entailed the process of developing an online questionnaire to determine awareness, knowledge, attitude and self-efficacy (AKAS) on healthy eating for nutrition education. Currently, there is no local validated questionnaire that can be used to assess AKAS on healthy eating among Filipino adults. Methods: The study developed the questionnaire based on theoretical frameworks and literature review. The draft questionnaire underwent three stages of development: (1) online modified Delphi technique composing of seven subject matter experts (SME) for content validity; (2) online cognitive debriefing with 32 participants (14 nutrition experts and 18 general public) for construct validity; and (3) online pre-testing with 35 participants (non-nutritionists) using test-retest method. Results: For first stage, the questionnaire contained 16 questions for awareness, 17 questions for knowledge, 17 questions for attitude, and 15 questions for self-efficacy. For second stage, significantly different scores (p-value<0.00) between nutritionist experts and general public were observed, showing good construct validity. For third stage, Spearman’s correlation of test-retest method was 0.640. The questionnaire yielded Cronbach’s alpha of 0.467 to 0.923 (round 1) and 0.435 to 0.923 (round 2). A second analysis was done to improve the internal consistency of the questionnaire. By combining two question categories (awareness and knowledge), the Cronbach’s alpha increased to 0.659 (round 2), and by deleting three questions in attitude category, the Cronbach’s alpha improved to 0.626 (round 2). Conclusion: The process used ensured the questionnaire’s validity and reliability. Hence, this online questionnaire may be adopted by parties interested in developing and assessing nutrition education.