[3][4] In 1557, Queen Bona Sforza of Poland made a loan to King Philip II of Spain, most of which was never repaid, despite Polish diplomatic efforts and requests (see Neapolitan sums).

[7] In 1936–1939, a number of Polish volunteers participated in the Spanish Civil War on the Republican side and were primarily assigned to the Dabrowski Battalion.

[8][9] During the Spanish Civil War, the Polish Embassy in Madrid provided shelter and asylum to more than 400 people, Poles and Spaniards, mostly fleeing from Republican forces, but some also from Nationalists.

[13] Honorary Consul of Poland in Valencia Vicente Noguera Bonora was murdered by pro-Republican communist militants just before his planned evacuation from Valencia in August 1936, to which both the Polish government and the Polish Embassy in Madrid responded with an official protest to the then- Republican Spanish authorities.

The Honorary Consulate of Poland in Barcelona organized temporary accommodation, false documents and transport for Polish civilians and military who fled from France to Spain in 1939–1942 with the intention of reaching the Polish-allied United Kingdom.

[18][19][20] In 1945, the German occupation of Poland ended and the country's independence was restored, although with a Soviet-installed puppet communist regime.

[21] After the Autumn of Nations and formation of a new, non-communist Polish government, both countries signed a Treaty of Friendship and Cooperation in 1992.

[7][22] April 12, 2010, was declared a day of national mourning in Spain to commemorate the 96 victims of the Smolensk air disaster, including Polish President Lech Kaczyński and his wife Maria Kaczyńska.

[3][25] Even more importantly, both countries also shared a strong Catholic history, on the frontier of struggles against Islamic conquest (Antemurale Christianitatis, Reconquista).