The goal of this study was to translate and adapt the Night Eating Questionnaire to Portuguese and assess the reliability of the Portuguese-language version. The study included two phases. The first consisted of: (1) translation into Portuguese; (2) back-translation into English; (3) correction and semantic adaptation; (4) content validation; and (5) assessment of the understanding of the questionnaire by means of 10 cm Visual Analogue Scales with 30 adult users of a nutritional support clinic. In the second phase, the questionnaire's reliability was assessed in 100 subjects with similar demographic characteristics to the first sample. In the fifth step, understanding of the instrument assessed by the visual analogue scales was 8.20+/-1.55 cm. The instrument showed satisfactory internal consistency, with an overall Cronbach alpha of 0.78. The Portuguese version proved to be easily understandable, with good semantic validation and consistency, suggesting that the questionnaire may be a good instrument for screening the night eating syndrome. However, other psychometric characteristics of this instrument need to be assessed in samples with different social and educational levels.