Post-harvested blackberry fruits were immediately treated with 1% and 2% calcium chloride by immersion at 20 ± 1^ºC for 2.5 min and kept for 8 days at 0 ± 0,5^ºC and Relative Humidity (RH) 90 ± 5%.  The application of calcium did not significantly effect on total titratable acidity, pH and   total soluble solids. The blackberry fruits treated with 1% and 2% Calcium chloride increased their ascorbic acid content by 15.7 and 37.5% respectively. Content of cyanidin-3-O-monoglucoside decreased by 6.33, 32.06 and 11.35 mg per 100 g of fruit in case of storage of untreated, treated with 1 and 2%   calcium chloride respectively. Content of pelargonidin 3 – O - monoglucoside increased respectively by 2.29, 26.87 and 8.45 mg per 100 g fruits. Change of content of cyanidin 3 – O - (6 - p – coumaroyl - glucoside) was not statistically significant.  Reduction in polyphenols content of control sample by 13.6% reflected in reduction of antioxidant potential by 25%. In the samples treated with 1 and 2%   calcium chloride reduction of polyphenols content by 12.4 and 7.5 % caused reduction of antioxidant potential by 15.6 and 8.7% respectively.