Correspondence (.75 linear ft.; 1915-1973) is arranged for the most part in chronological order, and includes a partial index to correspondents. Banér corresponded with family, friends, editors and other writers in both the United States and Sweden. There are letters in the collection from the following individuals: John V. Brennan, Paul Brooks, Maurice Evans, Dorothy Canfield Fisher, Oscar Hammerstein II, Ann Harding, Jean Hersholt, Ira R. Kent, Mary M. McBride, Agnes Moorehead, Frank L. Mott, Chase S. Osborn, Carl Sandburg, Leopold Stokowski, Edward Weeks, and Orson Welles.
Banér kept a separate file of letters from her friend Frederick T. Jeram; his earliest letters document his service in the First World War.
Nanna Banér Taylor donated correspondence concerning her sister, including letters from friends which she received in the years following Banér's death. These are filed as "Taylor" and "Washbourn" in the Correspondence series.