A wearable artificial kidney (WAK) is a device that continuously supports renal function during ambulation or social activities out of hospital. With the aim of improving dialysis patients’ quality of life, WAK systems have been in development for several decades. Technological evolutions in dialysis membrane and dialysate regeneration have been paving the way to wearability, and the possibility of implantation, for renal replacement therapies. However, at present, there are many technical issues confronting the attempts to apply WAK systems in clinical practice. Here, we have reviewed the necessary technical requirements and the WAKs currently being developed that are trying to meet these. Aside from technical issues, ethical, legal and economic aspects should be also considered together, in order to minimize trial and error in the development of the WAK. Continuous follow- up, integration with emerging new technologies, and multidisciplinary approaches involving clinicians, engineers, economists and social scientists are required for the realization of WAK in clinical practice.