Southall, who played 750 games for the Toffees and was capped 92 times by Wales, was one of the goalkeeping greats.
And in Manchester City star Hart, he sees a man whose self-belief is the key to his success.
Southall told The Sun: "When I first saw Joe playing for City, I didn't think he'd make it.
"He didn't have enough presence and looked small. But when he joined up with England, he just grew as a keeper.
"He thought, 'Yep, this is me'. If you compare that to Robert Green or Ben Foster or some others who have been in the squad, they give the impression they aren't sure it's for them.
"Joe's gone in there laughing and joking and taken to it like a duck to water.
"While others have been really tentative, he's gone in there, got on with it and made the position his.
"Joe wasn't bothered about the reputation of the great names before him like Banks, Shilton, Clemence or Seaman, that's what I liked about him. He is his own man."