Alexis Bledel arrives at the premiere of "Remembering Sunday" at Fox Studio Lot on April 17, 2013 in Century City, California. Credit: Gregg DeGuire/

Alexis Bledel's red carpet wardrobe just got even better! The 31-year-old actress attended the L.A. premiere of her TV movie, Remembering Sunday, on Wednesday, April 17 wearing her sizable new engagement ring from Mad Men costar Vincent Kartheiser -- and it's a beauty.

Bledel looked stunning in a black and white Pamela Roland cut-out dress, but all the focus was on her ring finger. The gorgeous ring features one massive round-cut diamond on a simple platinum band.

"Vincent picked it out," the Gilmore Girls alum gushed to Us Weekly on the carpet. Last month, Us broke the news that after nearly a year of dating, Kartheiser, 33, had popped the question.

Bledel, who guest-starred on season five of the AMC smash as the mentally unstable mistress of Kartheiser's character, Pete Campbell, said she'll be getting help from her future husband when it comes to planning their wedding.

"We're doing it together," she told Us. "We haven't started yet though."

When Us chatted with Kartheiser at the Season 6 premiere of Mad Men on March 20, the groom-to-be was still adjusting to the engagement. "I keep saying girlfriend," he said. "And then I'm like, 'I mean, my fiancee!'"

But the actor added, "I'm a very lucky man."