Assessing knowledge, self-efficacy, and practice among a given population us-ing a validated and reliable questionnaire is crucial. The aim of this study was to translate, validate, and test the reliability of the knowledge, self-efficacy, and practice in the Arabic population. Methods and Study De-sign: A previously published knowledge, self-efficacy, and practice nutrition questionnaire was translated and validated into Arabic. A panel of translation and nutrition experts from Arab countries participated in translation and testing validity. A convenience sampling technique was used to recruit participants across 22 Arab countries. An online self-administered questionnaire was completed twice with an interval of 2 weeks. Tests of validity (face and content) and reliability (consistency and test-retest reliability) were used. A total of 96 participants had a mean age of 21.5 years, 68.7% were female, and 80.2% were students. The mean expert proportional content validity index scale was 0.95, and intra class correlation values ranged from 0.59 to 0.76; all of these values were highly statistically significant at retest. The Arabic version of the questionnaire provided valid and reliable results for assessing knowledge, self-efficacy, and practice among Arab adolescents and young adults. This tool could assess nutritional education programs in a community setting and educational institutions targeting this population in Arab countries.