Russian tennis player Vera Zvonareva was blocked from entering Poland on Friday "for reasons of state security and public safety".
The former world number two, 38, was on the list of players set to compete at the Warsaw Open, starting on Monday.
But Poland's interior ministry said she is also on a list of people considered "undesirable" in the country.
Poland has become one of Ukraine's staunchest allies since it was invaded by Russia in February 2022.
The country has been refusing entry to people who support the actions of Russia and Belarus, however, Zvonareva had 'no war' written on her visor hat while playing at the Miami Open in March 2022.
"The Border Guard prevented a Russian tennis player from entering Poland," read a statement by the Polish interior ministry on Saturday.
"Vera Zvonareva, using a visa issued by France, tried to get into our country on a flight from Belgrade to Warsaw.
"After arriving from Serbia, the tennis player stayed in the transit zone of Warsaw Chopin Airport and today, after 12:00, she flew to Podgorica (Montenegro)."
The organisers of the Warsaw Open are yet to comment but the Women's Tennis Association said: "The WTA is aware of the situation involving Vera Zvonareva in Warsaw.
"The safety and wellbeing of all players is a top priority of the WTA. Vera has departed Poland and we will be evaluating the issue further with the event."
Russia's invasion of Ukraine has been supported by Belarus, which led to Russian and Belarusian athletes being banned from many sports.
Wimbledon followed other Grand Slam events by lifting its ban for this year's tournament, "subject to competing as neutral athletes".
Russian and Belarusian players continue to be asked about their stance on the war.