In this study, it was aimed to investigate the effect of the difference in the breeding environment (pH, temperature, salinity, oxygen content and saturation) of rainbow trout grown in dam and sea water on the level of some minerals (calcium, magnesium, zinc, iron) and biochemical parameters in the serum. The study material consisted of 20 rainbow trout (Oncorhynchus mykiss) weighing about 800-1000 gr in the dam water of Samsun (Derbent Dam) and the Black Sea water (Yakakent). Blood samples were taken from both groups on the same day in December and the pH, temperature, oxygen content and saturation level of the water were determined by YSK oxygen meter, and salinity was determined by refractometry. Total protein (TP), albumin (Alb), cholesterol (TK), glucose (Glu), urea, creatinine (Cre), uric acid (UA), Aspartate transaminase (AST), Alanine Aminotransferase (ALT), triglyceride (TG) Calcium, magnesium, iron and zinc and ALT, AST enzyme activities were determined by spectrophotometric method in an autoanalyzer. It was observed that the salinity, oxygen and saturation levels of the sea water were higher than those of the dam water, and the pH and temperature were close to each other. It was determined that TP, Alb, Alb/Glo, TK, TG, UA and Ca levels in rainbow trout raised in the dam were significantly higher than those raised in the sea (P<0.05). Glu, Cre, Mg and Fe levels were found to be higher in the blood serum of rainbow trout (P<0.05). Zn, urea, AST and ALT levels of rainbow trout raised in sea and dam were similar. In our study where the same fish species were provided with the same feeding conditions, it was observed that the differences in salinity and dissolved oxygen levels of fish farming waters caused changes in some mineral and blood parameter levels in fish. It was concluded that determining the supplementation of the missing minerals in fish according to the salinity and dissolved oxygen level in the environment may be important for the development of the fish.