For many allegedly confirmed pathogens it has never been experimentally confirmed that they really cause illnesses on hosts and result with inconvenient symptoms because infectivity trials have never been conducted. The aim of this paper is to review systematically the available literature on microorganisms that can be categorized as pathogens on freshwater Decapod crustaceans. I have analysed over 250 scientific publications where 214 microbe species (fungi/oomycetes, viruses, bacteria) were identified to potentially infect individuals from subphylum Crustacea and endanger their health and fitness. All recorded microbes were classified into three groups (pathogens, non-pathogens, and data deficient) depending on whether infectivity was successfully examined in laboratory-controlled environment. Diversity, ever-changing taxonomy and lack of research on microbial strains, along with misconception that each and every microorganism found in a dead crab is an agent of a disease, led to a small percentage of clearly confirmed pathogens only 13.55 % from a total number of the samples being studied). Considering importance of Decapod crustaceans in the food cycle freshwater ecosystems, but also in the economically viable aquaculture activities, the future research needs to be interdisciplinary in order to develop efficiently new methods of pathogen organisms identification. It is also necessary to conduct more frequents tests in order to reduce mortality outcomes of crab fauna, and preserve their populations.