Recent research has pointed to the need for addressing gender equality in parliaments in a broader perspective, focusing on gender sensitivity in parliaments in relation to structures, operations, methods and work. Up to now, however, the question of what it takes for this work to be long-lasting and sustainable has received limited attention. This article seeks to address this gap through a case study assessing the sustainability of the internal work of the Riksdag (the Swedish Parliament) with regard to gender equality, focusing on the durability and renewal of early initiatives and reforms. On the basis of Riksdag documents and interviews with MPs during the period 1994-2022, we ask: How sustainable is the internal gender equality work of the Riksdag with respect to the three key areas of representation, infrastructure and culture? We find that the Riksdag has managed to conduct sustainable gender equality work over the course of three decades. Major factors in this success are the institutionalization of a Gender Equality Group, the adoption of Action Plans for Gender Equality every parliamentary term and the legitimacy provided by the support of the Speaker of the Riksdag and the Riksdag Board.