When the Wehrmacht evacuated Wilna in 1944 in the face of the advancing Red Army, Plagge warned the forced labourers about the camp's imminent takeover by the SS, helping many escape. About 250 Jews survived the Holocaust thanks to the “saviour in uniform”. Since 2005, Plagge has been honoured as one of “The Righteous Among the Nations” at the Yad Vashem Memorial Centre in Israel.
Since May 2017, a new building of the TU in the Alexanderstraße bears the name “Karl Plagge House”.