"I think she is a great representative for this country, and a funny thing happens. She gets so unfairly maligned," said Trump. "The things they say, and I have known her for a long time, the things they say are so unfair."
Melania Trump has been falsely accused of working for an escort service -- a charge she defended herself against in court, winning one of the cases, and continuing her fight against another outlet.
"I`ll tell you this, she is going to be a fantastic first lady, she is going to be a tremendous representative of women," Trump said.
Trump added he has full confidence in his wife`s ability to handle the role, saying she feels "very, very strongly about women`s issues, women`s difficulties ... (she will be a) very, very strong advocate."
He also indicated Melania Trump will not be alone in her efforts.
"Helping her and working with her will be Ivanka (Trump), who is a fabulous person, and a fabulous, fabulous woman," he said. "They aren`t doing this for money, they aren`t doing this for pay, they are doing this because they feel it, both of them."
The President again confirmed the first lady, along with the couple`s 10-year-old son, Barron, will be moving to the White House when the youngest Trump finishes his school year in New York City.
"It is hard to take a child out of school with a few months left," Trump said.
On Wednesday, Melania Trump performed her first official duties at the White House, hosting the wife of Israel`s Prime Minister Benjamin Netanyahu, and accompanying her on a visit to the Smithsonian`s National Museum of African American History and Culture.
The first lady later tweeted out her thanks and appreciation, using a new hashtag that has so far accompanied a handful of her most recent tweets: #PowerOfTheFirstLady.