The Commission said economic sentiment in the 19 countries sharing the euro fell to 105.0 in January from a downwardly revised 106.7 in December. Economists polled by Reuters had expected a slight decline to 106.4.
The Commission's business climate indicator, which points to the phase of the business cycle, also fell to 0.29 from a downwardly revised 0.39 in December. Economists had expected a decline to 0.39 from the previously reported 0.41.
Sentiment in industry fell to -3.2 from -2.0, and declined to 11.6 from 12.8 in the services, which account for more than two thirds of the single currency area's GDP.
Consumers were less upbeat with their index at -6.3 in January, down from -5.7 in December.
Manufacturers became more downbeat about the possibility of raising prices in the future, with the selling price expectations index down at -4.2 from -3.2 in December and -0.8 in November.
Also consumers expected prices to grow more slowly in the next 12 months -- their inflation expectations index fell to 2.3 in January after holding at 3.6 in December and November.
The European Central Bank wants to accelerate inflation, now hovering at 0.2 percent year-on-year, to bring it closer to 2 percent and has been buying euro zone government bonds on the market to inject more cash into the economy.