December's reading, based on seasonally adjusted data, is the lowest since September 2014 when unemployment stood at 26.1 percent. The record high was set in September 2013, when unemployment hit 27.9 percent.
Joblessness has come down from record highs as the economy stabilised last year after a severe slump but it remains more than double the euro zone's average of 11.3 percent in December.
Greece's economy expanded by 0.7 percent last year, with recovery expected to gain traction this year.