The rate was one tick higher than December's 11.8 percent, the British Broadcasting Corporation reported Saturday.
The latest data from Greece is a month behind, but the highest unemployment rate in the currency region listed in the monthly report was 27 percent in November in Greece.
The lowest rate was in Austria in December, where unemployment stood at 4.9 percent.
High rates for January were also reported by Spain and Portugal, where unemployment was 26.2 percent and 17.6 percent, respectively.
Eurostat also said eurozone inflation had fallen to 1.8 percent, a two-year low that put the rate under the European Central Bank's target of 2 percent or less.
"All the data is supporting a rate cut, which we see in the second quarter," said economist Sarah Hewin from Standard Chartered, referring to the ECB's overnight bank to bank lending rate, which is currently 0.75 percent.
"They could move as early as next week, but there's an element of the ECB wanting to keep its powder dry as we enter an uncertain political situation with Italy and the Cypriot debt question has to be resolved," she said.