"Since February 24, a total of 9,044,000 people have crossed into Poland from Ukraine," it said in a tweet.
On Monday, around 29,600 refugees from Ukraine arrived in the country, according to the Polish Border Guard.
Meanwhile, more than 7.2 million people have left Poland for Ukraine since February 24, 2022, the agency also reported.
On Monday, around 20,400 people crossed from Poland into Ukraine, the Polish Border Guard said.
A deputy prime minister said last month that Poland was home to more than 2 million Ukrainians after many who had fled Russia's invasion moved on to other countries or decided to return to Ukraine.
Poland in March last year enacted a measure to offer wide-ranging support to Ukrainians escaping the Russian invasion of their country, which began on February 24, 2022.
The measure grants them residence rights and ensures access to education, healthcare and social benefits.
Eighty-three percent of Poles are in favour of accepting refugees from war-torn Ukraine, according to a survey published in December.