Background: Soil and plant contamination in copper exposure causes chronic copper poisoning (CCP) in animals following the consumption of plants in these soils. Objectives: The present study was carried out on 10 clinically affected copper poisoned cases (in each season) from autumn 2015 to the end of summer 2016, in four seasons in Kerman province to evaluate the seasonal effects of CCP in sheep. Methods: All samples were taken from clinically affected cases of copper poisoning that were then necropsied and the poisoning was confirmed by pathognomic pathological findings and serum copper concentration. Samples from liver, lung, kidney, heart and spleen were collected immediately after death and their copper concentration was measured. Results: The highest levels of copper in lung, heart, spleen and kidney were observed in the summer. Liver had the highest amounts of copper in spring and the levels of copper in wool and serum were detected in winter. The copper levels of liver and kidney were positively correlated in autumn, but the copper levels in these tissues were negatively correlated in both spring and winter. Conclusions: Severity of the copper toxicity (judged by the liver copper concentration) is season-dependent in sheep and seasonal variations affect this toxicity. Environmental climate and stressors may be the main causes of copper contents of different tissues and the liver is the main organ to reserve copper in poisoned sheep.