The Personal Correspondence subseries contains letters to and from Julius Berstl that were not specifically related to the business side of writing or theater. His correspondence ranges from fellow writers, to actors and people from the theater, to close friends. The letters range in date from 1901 to the end of Berstl's life in 1975. Just as there is a wide scope of dates, there is also a number of different topics included in Berstl's personal correspondence; they include picture postcards from friends talking about travel, letters to other authors discussing writing, and many more.

These letters were mostly found together originally; a small number of other personal letters have been classified under Personal and Biographical Documents or Theater Memorabilia due to their different original location or theme. Individual folder-level Scope and Contents notes list the majority of letters found in each folder along with their dates and the people involved.