The Theory of Authentic Leadership is based on philosophy and psychology as it proposes the establishment of more authentic organizations, with more conscious leaders and more transparent and ethical relations. The objective of this methodological study was to perform the cultural adaptation of the Authentic Leadership Questionnaire (ALQ) to Portuguese in the context of Brazilian Nursing. This instrument, originally written in English, has two versions, SELF and RATER: one assesses the authenticity of leaders and the other assesses the authenticity of those under leadership. ALQ has 16 items distributed into four domains: Relational Transparency; Moral Perspective and Ethics; Balanced Processing of Information; and Self-Awareness with statements answered on a four-point Likert scale: rarely/never (0 points), once in a while (1 point), sometimes (2 points), often (3 points), and very often, almost always (4 points). Hence, scores range from zero to 64; the higher the score, the more authentic a leader is. The adaptation process followed all the recommendations for methodological studies. Both versions (SELF and RATER) were initially translated to Portuguese and resulted in two other versions. An expert committee analyzed the versions and a synthesis of each version was obtained. These versions were then back translated and sent to the main author of the original ALQ. Changes were implemented according to the author's suggestion and the two versions were back translated once again. The syntheses were submitted to a second expert committee in order to ensure cultural, conceptual and idiomatic equivalences, resulting in the final version that was used in a pre-test. Face and content validity of all items of both versions was verified at this point by employing an inter-rater agreement of at least 80%. Both committees were composed of experts. The pre-test was applied to 80 nurses: 64 clinical nurses, eight supervisors, and seven nursing coordinators, who worked in various clinics of five hospitals located in two cities in the Midwest region of Brazil. Data were collected from June to August 2016. Afterwards, one of the instrument's authors certified that both versions were properly translated and adapted. Considering that the validation of an instrument is a cumulative process, the questionnaire in its two versions, SELF and RATER, should be submitted to new investigations in order to assess its psychometric properties and make available a valid and reliable instrument for researchers intending to acquire a better understanding in terms of authenticity of nurses working in Brazilian institutions.