Since the implementation of checkpoint inhibitors in the sequence therapy of metastatic bladder cancer just a few years ago, a new era for one of the most common tumor entities in Europe has begun. However, only a few studies on checkpoint therapy are available today. Most of these studies are phase-II, to some extent with small patient populations. This situation may cause a distortion in the estimated effects of immunotherapy or worst a distortion of the study results. Aim of this research project is the preparation of a Cochrane Review on immunotherapy for metastatic bladder cancer, which summarizes the current state of knowledge of this new therapy. Cochrane Reviews are internationally recognized as a quality standard in evidence-based medicine. According to the Cochrane guidelines, a systematic literature review, a systematic data extraction as well as data evaluation in terms of a meta-analysis will be carried out at the highest level of methodological quality. The scientific benefit of this Cochrane Review is a summary and evaluation of the currently available evidence. Compared to many individual studies, this evidence synthesis and -assessment helps to improve the trustworthiness of the estimated effects for the benefits or harms of an immunotherapy for metastatic bladder cancer. As a clinical benefit, these results will help to better quantify the effects and impairments of immunotherapy on affected patients. Due to the implementation of this Cochrane Review into clinical routine (e.g. guidelines), patient’s treatment should be improved.