As far as I can remember, the books don't really analyze this question. However, there are a few points that may have helped Harry believing Hagrid:* Hagrid's personality may have helped.
* Hagrid himself is "unbelievable", being a half-giant.
* Hagrid did some magic himself.
* The letter from Hogwarts.
* Uncle Vernon's reaction to Hagrid wanting to tell Harry the truth.
* Harry's previous experiences with magic (he had accidentally done magic, now and then).
Rubeus Hagrid.
Hagrid decided to buy Harry's animal and gift it to him as a birthday present. Hagrid is allergic to cats as they make him sneeze and Toads were old fashioned, students would have laughed at and made fun of Harry and Hagrid didn't want that
The Actor Robbie Coltrane portrays the character Hagrid in the Harry Potter Film Series.
huge
Lily Luna Potter, Harry's daughter, would have grown up knowing because all her family would be magical. Lily Evans, Harry's mother, was told by Severus Snape and it was confirmed by her Hogwarts letter. Somebody would have come and explained it to her parents like Hagrid did with Harry (only they thought he knew).
Hagrid got Harry a pet owl named Hedwig.
Among the many facts that Harry Potter learned from Rubeus Hagrid are that Harry is a wizard and that his parents were not killed in a car crash, but murdered by Lord Voldemort. Throughout his years at Hogwarts, Harry learns others things from Hagrid who becomes his Care of Magical Creatures professor for three years.
Hagrid left Harry with his relatives, the Dursley's, who live in Surrey.
On Lego Harry Potter, Hagrid's beard is black.
Rubeus Hagrid.
No Hagrid never dies.
Robbie Coltrane plays Rubeus Hagrid on the Harry Potter movies he was quite the character.
HAGRID'S name is Rubeus Hagrid.
Hagrid decided to buy Harry's animal and gift it to him as a birthday present. Hagrid is allergic to cats as they make him sneeze and Toads were old fashioned, students would have laughed at and made fun of Harry and Hagrid didn't want that
Hagrid was a character from the Harry Potter series. While Hagrid was sent to prison and in hiding at times, he did not die during the series.
Well Hagrid wasn't extremely sentimental for Harry, he also only named his children after dead people and Hagrid was still alive when he his kids.
during the 7th harry potter book when hagrid and harry are traveling to the burrow hagrid presses this button that makes the flying motorcycle spin and the firebolt, Hedwig, and other things of harry fall to the ground. (harry is able to catch Hedwig's cage but not before it is hitting by a curse, in result killing Hedwig)