Main canon ---------- Within the main canon, we **simply don't know.** **Guesswork:** Like Harry, he certain isn't fond of dementors and a very common boggart form among his contemporaries is Lord Voldemort. He also has several friends (Dumbledore, notably) and a close relative (Grawp) that he wouldn't want to see their corpses. ---------- Lower-canon speculation. ------------------------ The [Official Harry Potter Bloomsbury Website][1] contains a quiz about "your Hogwarts best friend" in which we learn the main fears of various characters, including Hagrid. Assuming these fears also represent the person's boggart form, Hagrid's would be **Azkaban Prison.** [![enter image description here][2]][2] [1]: http://www.harrypotter.bloomsbury.com/uk/fun-stuff/who-is-your-hogwarts-best-friend/#hpq-top [2]: https://i.sstatic.net/q46tv.png