Sources exclusively tell E! News that the two plan to tie the knot in a "weekend affair" in the Magic Mike star's home state of Texas.
Alves was to be honored today by the Step Up Women's Network at a posh Beverly Hills luncheon but instead she will deliver her remarks via video, allowing her to be close to home for the wedding preparations.
The private couple apparently has invited just two dozen close friends and family members for what promises to be a cozy celebration.
We're told that workers involved with the top-secret nuptials have had to sign nondisclosure agreements.
A rep for the couple could not be reached for comment.
The 42-year-old actor and the 30-year-old Brazilian model and handbag designer got engaged during the holidays, when he popped the question on Christmas Day.
"Just asked Camila to marry me, Merry Christmas," McConaughey announced on his WhoSay page.
The couple, who began dating in 2006, have two children, 2-year-old daughter Vida and son Levi, who turns 4 next month.
The family recently relocated from the L.A. area to Austin. "I grew up here," McConaughey told us in March in Austin at the South by Southwest premiere of his film Killer Joe. "We got children, family values, neighbors and common sense."
Congrats, you two!