AIM: To develop and validate a questionnaire to evaluate knowledge, attitude and practice of patients diagnosed with age-related macular degeneration (AMD) who have undergone intravitreal injection treatment. METHODS: This study was conducted among patients diagnosed with AMD in Kuala Lumpur. The generation of the instrument included four phases which included item and domains development, content, face validity and exploratory factor analysis. Content validity and modified Kappa was used for validation of knowledge domain. Exploratory factor analysis was used for validation of both attitude and practice domains. Face validity was conducted in 12 patients, content validity was ascertained in 120 patients and test-retest reliability was determined in 39 patients with AMD. RESULTS: Content validity index (CVI) and modified kappa showed excellent values for most items in the knowledge domain with CVI for item (I-CVI) values between 0.78-1.0 and Kappa values of >0.74. The Kaiser-Meyer-Olkin (KMO) sampling adequacy showed acceptable scores of 0.70 and 0.75 for both attitude and practice domains respectively and Bartlett’s Test of sphericity were significant (χ2=0.00, P<0.001). Factor analysis resulted in five factors with thirty items for attitude domain and four factors with twenty items for practice domain. The Cronbach’s alpha showed acceptable values for all items in knowledge, attitude and practice domain with values >0.70 and good test-retest reliability. The final version of the questionnaire consisted of 93 items from four sections consisting of demographic details, knowledge, attitude and practice. CONCLUSION: The findings of this validation and reliability study show that the developed questionnaire has a satisfactory psychometric property for measuring KAP of patients diagnosed with AMD undergoing intravitreal injection treatment.