Coldwater aquaculture plays a crucial role in meeting the growing need for fish as a source of food. However, one of the major problems faced by the coldwater aquaculture industry is the frequent outbreak of infectious diseases. Poor environmental conditions, low water temperature, and bad water quality also contribute to disease outbreaks by weakening the fish immune system. The increased expansion of aquaculture operations has significantly increased the likelihood of disease outbreaks and their rapid spread. Therefore, it is crucial to understand the multiple factors that contribute to the occurrence and transmission of diseases to ensure successful management and sustainability in coldwater aquaculture. This chapter focuses on the common fish diseases prevalent in coldwater aquaculture, associated pathology, and subsequent control measures.