These include drawings by Michał Elwiro Andriolli and a pastel painting by Teodor Axentowicz that had been believed destroyed during the war.
Before the war, these works were part of the collection of the Warsaw-based Society for the Encouragement of Fine Arts, Poland’s Culture Minister Piotr Gliński said during a press conference on Thursday.
He added that recovering the works took almost a decade due to complicated legal procedures.
The recovered works include Lady in Peacock Feathers by Axentowicz, a painter, illustrator and graphic artist who was one of the leading representatives of the Young Poland art movement inspired by Polish folklore.
Born in 1858 in Romania, he died in the southern Polish city of Kraków in 1938.
The National Museum has also acquired illustrations to the novel Maria by Antoni Malczewski.
But only five of the eight illustrations by Andriolli have been recovered.
Andriolli, born in 1836, was a Polish painter and architect of Italian descent. He is best remembered for his illustrations to the Polish national epic Pan Tadeusz by Adam Mickiewicz, as well as for his distinctive style of architecture known as the Świdermajer. It was especially popular in villas built on the outskirts of Warsaw.
The latest acquisition by Warsaw's National Museum is yet another example of efforts to recover valuable works of art from Polish collections that went missing during WW II.
The effort is in large part driven by the Polish Ministry of Culture and National Heritage and involves a painstaking search for lost objects of art based on a catalogue compiled by officials.
Among the many initiatives making up the project is a virtual Lost Museum that aims to preserve the memory of works of art that perished or were looted during wars, especially WW II, and encourages the public to rediscover forgotten masterpieces.