"For the sake of their children, they ask for respect and privacy as they navigate this time in their lives," her rep says.
Harmon, who stars in the TNT drama Rizzoli & Isles, and the former NFL player got engaged on The Tonight Show with Jay Leno in 1998, after Sehorn surprised Harmon by walking out onto the set and getting down on one knee.
They went on to have three daughters: Finley, 11, Avery, 9, and Emery, 5.
"We don't get out Friday nights early enough to catch a flight home," she told Your Tango. "So I'm here [in L.A.]. We sometimes meet in Texas, a 2½-hour flight for both of us. I miss my kids, so it's hard, but my children are so understanding."
The former Law & Order star also admitted she and Sehorn, 43, strived to keep their marriage strong despite the distance.
"You have to be really considerate of each other, really kind to each other," she said. "It's a lot of work."