Jennifer Garner is moving on! Literally, moving ...

The actress recently sold her Pacific Palisades home she shared with ex Ben Affleck to Adam Levine and Behati Prinsloo for $32M because, SURPRISE!, she building her OWN dream home in nearby Brentwood.

X17online can report EXCLUSIVELY that Jen is just months away from moving into her own, significantly smaller custom estate about a quarter of a mile down the street from where she and the kids live now.

The mother-of-three will be close the westside hotspot Brentwood Country Mart and all of Jen's favorite exercise studios. She's count LeBron James and other celebs as neighbors in this picturesque area of LA's most exclusive zip code.

Garner hired architect-to-the-stars Ken Ungar who designed her pal Reese Witherspoon's Palisades mansion. The move will be a downsize for Jen -- going from a whopping 16,000 square feet on 3.1 acres to a 1/3rd of an acre and what appears to be about 8500 square feet of living space in her new abode.

Jen snatched up the lot last July for $6.5 million and broke ground on her new place shortly thereafter. The new home, a traditional Cape Cod, will be home to her three kids Violet, Seraphina, and Samuel -- convenient to the younger kids' school just down the street -- and close to Violet's bus stop for her all-girls private middle-school/high-school across town.

Jen and the kids are expected to move into their new estate over the summer. We imagine boyfriend John Miller will be spending some time there, too!