Greece's annual EU-harmonized inflation rate turned negative in January after the first positive reading in the previous month that halted 33 straight months of deflation, data from the country's statistics service showed on Wednesday.
January's print of -0.1 percent was below market expectations. Economists polled by Reuters had forecast a 0.3 percent rate after December's 0.4 percent.
The data showed the headline consumer price index fell 0.7 percent year-on-year in January, with the annual pace of deflation accelerating from the previous month.
Consumer prices were led lower by apparel and footwear, durable goods and housing costs due to the fall in heating oil costs.
For years an inflation outlier in the eurozone, Greece had been in deflation mode for the last two and a half years as wage and pension cuts and a protracted recession took a heavy toll on Greek households' income.
Deflation in Greece, which signed up to its first international bailout in 2010, hit its highest level in November 2013, when consumer prices registered a 2.9 percent year-on-year decline.
Inflation in the 19 countries sharing the euro rose to 0.4 percent year-on-year in January from 0.2 percent in December, based on Eurostat estimates.