Industrial production in the 16 countries that use the euro increased for the third consecutive month in May.
Eurostat, the EU's statistics office, said production climbed by 0.9% from the previous month, the same as the increase seen in April.
However, economists had forecast a rise of 1.2%.
Eurozone manufacturers have benefited from the lower value of the euro, as this makes their goods cheaper in countries outside the bloc.
This has helped manufacturers play a key role in dragging the EU out of recession.