Sales receipts in the 17-nation eurozone fell 0.3 percent, while sales in the 27-member European Union dropped 0.27 percent, Eurostat said.
Sales also fell from August 2010 -- by 1 percent in the eurozone and by 0.8 percent in the European Union -- Eurostat said.
In August, sales of food, drinks and tobacco rose in both regions, while sales of non-food items decreased.
Food sales were up 0.2 percent in the eurozone and 0.5 percent in the European Union. Non-food sales fell 1.3 percent and 0.7 percent, respectively.
Nationally, retail sales dropped furthest in Malta, where sales fell 8.8 percent on an annual basis. Sales rose farthest in Luxembourg, rising 11.7 percent, Eurostat said.