Speaking to reporters on a conference call, Trump explained that he expected the Real Housewives of New Jersey star to be "a total wild woman".
"She's much different," he said. "She's a very quality person. She's much different than I thought she would be... I mean, she's more reserved if anything else, and I think it's a lot different than when you see her on the other show."
Trump suggested that it could be "rebranding" or that "she is a little bit intimidated by some of the other people".
"She is more quiet than I would have thought she would have been," he continued. "She's a little bit of a surprise... I don't mean a negative surprise, but it's surprising to me that she's not more volatile."
Trump revealed that Giudice does have some "crazy moments" ahead, but added: "Still, she's more quiet than I would have thought, more subdued."
Trump has previously described Giudice as "a very calm person... until she gets angry".
The Celebrity Apprentice airs on Sundays at 9/8c on NBC.
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