No, 13 Reasons Why is not based on a true-life story. The TV series is based on a novel titled Thirteen Reasons Why. The novel was written by Jay Asher, and it was written in 2007.
The novel tells the story of a high school student, Hannah Baker, that committed suicide because of the betrayal and bully that came upon her.
The first season of the series followed the book closely, but the remaining seasons do not follow as the book does not have a sequel.
The storyline and many other casts were added to the television series.
The author of the book, Jay, has also revealed that characters and the story are not real.