Retailers' sales declined by 0.4 percent in October compared with September, the federal statistics office Destatis said in a statement.
The previous month, retail sales had stagnated.
On a 12-month basis, however, business increased strongly, jumping by 2.1 percent in October compared with the same month last year, the statisticians calculated.
Retail sales data are often revised.
Last week, a leading consumer sentiment survey, conducted by the GfK market research institute, found that consumers are beginning to worry about the economic consequences of the huge influx of migrants in Europe's refugee crisis.