Resumen: A good level of nutrition literacy (NL) is proposed as a determinant factor for following a healthy diet. Improving seniors’ NL might be particularly pertinent to enhance the quality of their diets. This study aimed to systematically design and validate a short seniors-oriented questionnaire as a screening tool to evaluate NL. We developed the Myths-NL questionnaire, composed of 10 widespread nutrition myths, and checked for its content and face validity. An observational cross-sectional study was conducted to explore the validity and the test–retest reliability, involving a community-dwelling group of 316 individuals aged 65 years and over. Construct validity was proved by establishing both discriminant and convergent validity. Cronbach a = 0.61 and Spearman r = 0.79 (p = 0.02) demonstrated internal consistency and test–retest reliability. Participants who had secondary/university studies scored significantly higher compared with those with primary (p < 0.001), and a significant linear relationship (R2 = 0.044, p = 0.001) with a positive slope (ß = 0.209) between Mediterranean Diet Adherence Screener (MEDAS) and Myths-NL scores was observed, proving construct validity. In conclusion, the Myths-NL questionnaire is a valid and reliable tool to screen NL in Spanish seniors and it might be useful as an assessment NL tool for designing and implementing lifestyle interventions to promote healthy eating. Idioma: Inglés DOI: 10.3390/ijerph182212107 Año: 2021 Publicado en: International journal of environmental research and public health 18, 22 (2021), 12107 [11 pp] ISSN: 1661-7827 Factor impacto JCR: 4.614 (2021) Categ. JCR: PUBLIC, ENVIRONMENTAL & OCCUPATIONAL HEALTH rank: 45 / 182 = 0.247 (2021) - Q1 - T1 Categ. JCR: PUBLIC, ENVIRONMENTAL & OCCUPATIONAL HEALTH rank: 71 / 210 = 0.338 (2021) - Q2 - T2 Categ. JCR: ENVIRONMENTAL SCIENCES rank: 100 / 279 = 0.358 (2021) - Q2 - T2 Factor impacto CITESCORE: 4.5 - Medicine (Q2) - Environmental Science (Q2)