"Since February 24, a total of 6.46 million people have crossed into Poland from Ukraine," it said in a tweet.
On Wednesday, around 23,000 refugees from Ukraine arrived in the country, according to the Polish Border Guard.
Meanwhile, more than 4.68 million people have left Poland for Ukraine since February 24, the agency also reported.
On Wednesday, some 24,000 people crossed from Poland into Ukraine, the Polish Border Guard said.
A deputy interior minister said last week that Poland was home to some 1.3 million Ukrainians after many refugees from Russia's invasion of Ukraine decided to return to their country.
Poland in March enacted a measure to offer wide-ranging support to Ukrainians escaping the Russian invasion of their country, which began on February 24.
The measure grants them residence rights and ensures access to education, healthcare and social benefits.
Eighty-one percent of Poles are in favour of accepting refugees from war-torn Ukraine, according to a recent survey.