This study was conducted to investigate the effects of periods of starvation and refeeding on some hematological, serum parameters and whole body proximate composition in Caspian salmon (Salmo trutta caspius). 240 samples of the Caspian salmon with an average weight of 13.73 ± 0.63 g were kept in 300 liter polyethylene tanks. Samples were fed twice a day with Rainbow trout commercial feed to the point of satiation. This experiment lasted for 10 weeks with control (without starvation) and 3 starvation treatments including 2, 4 and 6 weeks of starvation followed by 4 weeks of refeeding with 3 replicates. During rearing period, the average of water temperature, pH and dissolved oxygen were 14.15±0.27 ° C, 8.44±0.17 and 6.34±0.24 mgl^-1, respectively. At the end of starvation period, the results of blood parameters showed that starvation significantly increased red blood cells and hematocrit in treatment with 2 weeks of starvation (0.893±0.58 × 10⁶/mm³) and 6 weeks of starvation (42.33±3.21 %, P<0.05), respectively. At the end of trial, the highest value of white blood cells belonged to 6 weeks starvation treatment (14.2±0.12 × 10³/mm³) while the lowest (10±0.60 × 10³/mm³) was observed in the control. Results of the biochemical serum parameters indicated the lowest amount of total protein (1.71±0.88 mg/dl) and glucose (41.35±1.44 mg/dl) were obtained in 6 weeks starvation treatment, right after the starvation period (P<0.05). At the end of the starvation period, the whole body protein content of control was lower than other treatmens (P<0.05), but after 2 weeks of refeeding, whole body protein content of 2 and 4 weeks starvation treatments didn't show any significant difference compared to control (P>0.05). At the end of the experiment, the lowest value of lipid belonged to starvation treatments while the highest value was observed in control (P<0.05). Generally, this can be inferred that Caspian salmon fish can tolerate starvation for 2 weeks without any negative impact on blood and serum biochemical parameters and for 4 weeks on whole body proximate composition.