The former Baywatch star said that in one instance he even helped a boy come out of a coma with a recording of his voice.
Speaking on Richard Bacon's BBC Radio 5Live show, the actor and singer said: "The upside of being in showbiz is being able to hold the hand of a kid who is dying, you know.
"I did a tape for a kid saying, 'Hey buddy, it's Michael Knight, Michael Knight, come on, wake up, wake up, wake up'. The phone rang and they said, 'Remember that kid you did the tape for that was hit at that crosswalk in London? Well we played the tape for him and he came out of the coma'."
He added: "I don't want to be corny or anything but that's happened to me a thousand times all around the world because it can affect people in a positive way."
Hasselhoff is currently promoting his family's reality series The Hasselhoffs, which starts on Bio next month.
> David Hasselhoff: 'I'd like to remake Lovejoy'