The 50-year-old actor recalled the moment he first saw the Brazilian-American model, 38, during Monday's episode of Good Morning America.
McConaughey said he "can't say" he immediately knew Alves was "the one" but shared his sense of awe.
"She was moving to my right to left across a room and it did not look like she was walking, meaning her head was not bobbing. She was more floating," the star recounted. "I did not say, 'Who is that?' I said, 'What is that?'"
"I just saw her move. It was just four seconds of her moving," he said. "I will say this, every beautiful thing that went through my mind about who and what she was, she has turned out to be exactly that and then some."
McConaughey said he "knew right away that she was something special."
"Then very soon over the next years, when we really fell in love and I knew that this is the woman I want to spend the rest of my life with," he added.
McConaughey and Alves married in June 2012 and have three children, daughter Vida, 10, and sons Levi, 12, and Livingston, 7. McConaughey said on Today in April that his family has been doing a lot of cooking and cleaning during the COVID-19 pandemic.
"We're in the kitchen for about four and a half hours a day. We don't have any idle time. I'll tell you that. Zero idle time," he said.
McConaughey further discusses his relationship with Alves in his memoir, Greenlights, slated for release Tuesday. On GMA, McConaughey said Alves urged him to write the book.
"Finally, I got a little bit of time on my hands and a kick in the backside by my wife, which she does so well, and she said, 'Get out of here and don't come back home till you got something,'" he said. "And what I found was what you got in this book."
McConaughey most recently appeared in the Guy Ritchie film The Gentlemen.