In her first one-to-one sit down interview as First Lady, Melania spoke of her disgust at seeing the images of children kept in large pens without their parents.
The separation policy caused widespread anger across the US and was condemned by both Democrats and Republicans.
Speaking to ABC, Mrs Trump said: “I saw it on the news and I reacted right away.
“It was unacceptable for me to see children and parents separated.
“It was heartbreaking. And I reacted with my own voice. I went to the border.”
Furious at not having been aware of the policy’s implementation, the First Lady accused her husband of “blindsiding” her over the tough stance.
She said: “I didn’t know that policy would come out. I was blindsided.
“I told him that I thought it was unacceptable and he felt the same.”
Melania spoke out against the policy at the time through her spokeswoman, claiming she “hates to see children separated from their families”.
Communications director, Stephanie Grisham, said: “She believes we need to be a country that follows all laws, but also a country that governs with heart.”
Explaining in her one-to-one sit down what she would say to any families still separated the First Lady added: “I would tell them to keep strong and that time will come, everything needs to go through the court system.”
Melania also explained in the interview why she wore her controversial coat, which was emblazoned with the slogan “I don’t care”, when she visited migrant children at the US-Mexico border in June.
She said she for the people and “for the left-wing media who are criticising me”.
She added: “I want to show them that I don’t care.
“I would prefer that they would focus on what I do and on my initiatives rather than what I wear.”