Weixlgärtner was born on 6 April 1872 in Vienna in an artistic family; his father a Hungarian count and his grandfather a landscape painter.
He grew close to his brother-in-law, the famous modern architect Richard Neutra, 20 years his junior, whom he mentored and assisted in his cultural development.
[a][4][1] His wife, Pepi, had Jewish ancestry,[2] which the Nazi regime would not tolerate, and furthermore, he refused to hand over the keys of the Treasury to the SS.
[1] In April 1945, at the very end of World War II, the Nazis burnt down his house[2] and he lost all his belongings, including his large library of art history literature, his private collections, and an academic manuscript ready for printing together with the rest of his property; according to his obituary, "he was not able to save even his everyday clothes".
[1] He wrote a large number of academic publications, among them a monograph on Austrian painter August von Pettenkofen,[4] a monograph about the Reliquary of St. Elizabeth,[1] a Festschrift for fellow art historian Julius von Schlosser,[2] a thesis about Matthias Grünewald and Albrecht Dürer,[1] and more.