The federal lawsuit says he took the material for a book called "Kate Gosselin: How She Fooled the World."
The suit, filed Monday in Philadelphia, says the book was written by her ex-husband's friend, tabloid writer Robert Hoffman, but has since been pulled from Amazon because the material was obtained illegally.
The couple starred in the TV show "Jon & Kate Plus 8," detailing life with their twins and sextuplets, before they separated in 2009 and later divorced.
She lives in Sinking Spring, while he lives in Wyomissing. Both are in Berks County, outside Philadelphia.
A lawyer who once represented Jon Gosselin did not immediately return a message seeking comment.