The latest jobless figure came in a notch lower than an earlier estimate of 5.9 percent by the labour ministry.
There were around 909,500 people without jobs nationwide at the end of August, up from 906,400 a month earlier, according to the state-run Statistics Poland (GUS) agency.
The statistics office reported earlier this week that employment in Polish companies dropped by 0.8 percent in August on average in year-on-year terms.
According to the European Union's Eurostat statistics agency, which uses a different methodology, unemployment in Poland had stood at 3.4 percent in July, marking the second-lowest rate in the 27-nation bloc.
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Source: IAR/PAP