The official opening of the renovated premises will take place during Polish Foreign Minister Jacek Czaputowicz's visit to the Lithuanian capital on Thursday.
Poland's consulate and the Polish Institute in Vilnius are also moving into the building.
"We are happy that the beautiful city of Vilnius has received new historic, reconstructed buildings that will be a delightful sight for passers-by and tourists," Urszula Doroszewska, the Polish ambassador to Lithuania, said at a news conference in the palace's former ballroom on Wednesday.
The history of the former palace of the Pac family, one of the most influential noble families in the Grand Duchy of Lithuania, dates back to 1628 when several small houses on the land plot were sold to Vice-Grand Chancellor of Lithuania Steponas Kristupas Pacas (Stefan Krzysztof Pac).
The houses were later combined into one large building, which has since repeatedly changed owners and has been repeatedly rebuilt and renovated.
Poland invested 18 million euros in the renovation, which took almost two years and a half to complete, contractors said.
Doroszewska said that the embassy will seek that the renovated palace can be visited by as many people as possible.