The object of this paper is the ultra-activity of collective agreements after ex-piration in the brazilian and portuguese legal systems, presenting the concepts, address-ing the historical evolution of labor legislation and jurisprudence, as well as the confron-tation of the current regime with the Constitution of the Portugal and the Constitution of the Brazil, emphasizing the decisions handed down by the portuguese Constitutional Court, by the brazilian Federal Supreme Court and recent legislative changes. Relevant to also note the problem of rights acquired by the working class in the face of the expiration of the collective agreements, as well as the questions raised about the contradiction be-tween the sense and necessity of the promotion and dynamism of collective bargaining.