Crustaceans during a parasitism relationship with fish cause biological disruption and diseases to the hosting fish that threaten their life. Several crustacean groups were reported to parasitize different fish species as definitive hosts. Copepods, Isopods, and Branchiura are the major fish parasitic groups under the crustacea. They are mainly ectoparasites and occasionally, the small and microscopic members can infest the internal organs of their fish hosts. The infected fish are suffering from serious clinical signs and the infested organs are usually suffering from severe pathological disruptions and lesions. Treatment is taking place by several chemical and biological facilities. Here in the current article, the major crustaceans that parasitize on fish are reviewed by describing their corresponding harms to the hosting fish. Factors affecting the prevalence of the crustacean parasites and some of their hazardous effects on the infected fish were considered.  In addition, trials for the chemical and biological control of the crustacean infestations are summarized.