This article intends to reflect and to deepen the topic of Secrecy, equated as a moral duty / professional obligation. Throughout the work an historical view of the concept's evolution is shown, since its foundation, until its current representation in the practice of the Nursing profession. Concomitantly to this evolutive description, an approach is carried through the concepts that are underlying the concept of Secrecy, namely: privacy, confidentiality and intimacy. The topic of secrecy is, also, analyzed under a deontological and legal perspective, distinguished in the Nursing domain and focused on the nurse's practice.