This film is based on the book by Gregory McDonald, which is the second book in the Fletch series. Assassinato por Encomenda (1985) starring Chevy Chase was based on the first book.
Fletch says he quit journalism because the profession has been cheapened by social media. In the book, Fletch has retired and fled the US having secured a large amount of money from a corrupt businessman (as depicted in the original 'Fletch' novel/film).
In a 2022 interview with The Upcoming, Greg Mottola, who is a huge fan of the original film, spoke about his particular vision for the character and why he wanted to make the movie: "When the script came in, it was a very funny script, but it felt like a script for Chevy Chase. Zev Borow, who is a great writer and a great guy, really loves the original Assassinato por Encomenda (1985) and couldn't stop himself from kind of writing 'Fletch 3'. And Jon Hamm and I said well this is great, but it's not really the tone we wanted. So I did the next pass on the script and brought it closer to the book and brought in more characters from the book and more plot from the book. Still setting it in contemporary times, so a lot of things had to be the modern equivalent to what was a '70s-vibe character or a bit of social satire from the novel. To me it was a dream come true to do a detective movie, because that's really what all the novels are. It's just Gregory McDonald cast an investigative journalist in the detective role. I love those movies. I'm a huge fan of O Falcão Maltês (1941) and O Perigoso Adeus (1973) and À beira do abismo (1946), the genre in general. So I was very excited to do it."
Tasserly pretends he needed medication to treat a condition he calls "Segegenesis". In his struggle to lie on the spot, he just altered the name of the classic console video game system Sega Genesis.
The character of Frank Jaffe does not appear in the novel 'Confess, Fletch'. He was a former editor of Fletch's, but he never worked in Boston.