Consumer inflation slowed to 1.4 percent year-on-year last month, below the 1.7 percent forecast of analysts polled by Reuters and below the lower bound of the central bank's inflation target. The data was below all forecasts.
"The inflation data published today strengthens the proponents of a stabilisation in interest rates," Bank Millennium said in a note, adding it signalled slightly lower inflation ahead, but would not affect core inflation much.
The central bank targets inflation at 2.5 percent with a symmetrical band of plus or minus one percentage point.
Following the data, Poland's currency, the zloty, weakened by 0.4 percent. It traded at 4.2160 by 1010 GMT.
Derivatives markets showed reduced expectations interest rates will rise. The first 25-basis-point rate increase was fully priced in only over the next 18 months. Analysts polled earlier by Reuters expected it in 12 months.
The central bank has kept its main rate at 1.50 percent since a 50-basis-point cut in March 2015.