Ali Larter and Hayes MacArthur welcome second child!
Ali Larter seen at eOne Films US Premiere of "You're Not You" on Wed, Oct 8, 2014, in Los Angeles. (Photo by Alexandra Wyman/Invision for eOne Films US/AP Images)
LOS ANGELES, CA - NOVEMBER 16: Actress Ali Larter is seen on November 16, 2014 in Los Angeles, California. (Photo by JMA/Star Max/GC Images)
Expectant actress Ali Larter arrives at the Pampers #BabyGotMoves event at the Children's Museum of Manhattan, Wednesday, Aug. 20, 2014, in New York. Parents can post videos of their little ones' best morning moves using #babygotmoves or #bebeconritmo and it may be featured in a Pampers video. (Photo by Diane Bondareff/Invision for Pampers/AP Images)
NEW YORK, NY - AUGUST 7: Ali Larter at NBC's Today Show promoting her new TNT TV series Legends on August 7, 2014 in New York City. Credit: RW/MediaPunch/IPX
Actors Angie Harmon, left, and Ali Larter pose backstage at the TNT and TBS Network 2014 Upfront Presentations at Madison Square Garden on Wednesday, May 14, 2014, in New York. (Photo by Evan Agostini/Invision/AP)
Actress Ali Larter poses at The Art of Elysium's Heaven Gala on Saturday, Jan. 11, 2014, in Los Angeles. (Photo by Chris Pizzello/Invision/AP)
IMAGE DISTRIBUTED FOR ENTERTAINMENT WEEKLY - Ali Larter attends the 2013 Entertainment Weekly Pre-Emmy Party, presented by L'Oreal Paris and bebe at Fig & Olive on Friday, Sept. 20, 2013, in Los Angeles. (Photo by Alexandra Wyman/Invision for Entertainment Weekly/AP Images)
Actress Ali Larter arrives at the LA Food and Wine Festival's Festa Italiana with Giada de Laurentiis on Thursday, Aug. 22, 2013 in Los Angeles. (Photo by Paul A. Hebert/Invision/AP)
Actors Sean Bean, left, and Ali Larter attend the TNT and TBS 2013 Upfront at the Hammerstein Ballroom on Wednesday, May 15, 2013 in New York. (Photo by Evan Agostini/Invision/AP)
Ali Larter, right, and Hayes MacArthur arrive at the 24th Annual GLAAD Media Awards at the JW Marriott on Saturday, April 20, 2013 in Los Angeles. (Photo by Jordan Strauss/Invision/AP)
Ali Larter and Hayes MacArthur attend the LA Art Show hosted by Ali Larter and Hayes MacArthur Benefiting the Art of Elysium at the LA Convention Center on Wednesday, Jan. 23, 2013, in Los Angeles. (Photo by Todd Williamson/Invision/AP)
Ali Larter attends the first annual Baby2Baby Gala in Los Angeles on Saturday Nov. 3, 2012. Baby2Baby hosted the gala to raise awareness and funds for the Los Angeles based non-profit organization. (Photo by John Shearer/Invision/AP)
Ali Larter attends the "Bachelorette" premiere at Arclight Cinemas on Thursday, Aug. 23, 2012, in Los Angeles. "Bachelorette" will be released in theaters Friday, Sept. 7, 2012. (Photo by John Shearer/Invision/AP)
Actress Ali Larter attends Good Housekeeping's 'Shine On' Women Making History theatrical event at Radio City Music Hall on Tuesday, April 12, 2011 in New York. (AP Photo/Evan Agostini)
Actress Ali Larter arrives for amfAR's Inspiration Gala Los Angeles, Wednesday, Oct. 27, 2010, in Los Angeles. (AP Photo/Chris Pizzello)
Ali Larter arrives at the premiere of "Secretariat" in Los Angeles, Thursday, Sept. 30, 2010. (AP Photo/Matt Sayles)
Actress Ali Larter arrives for the Opening Night Gala for KOOZA, the big top touring show from Cirque du Soleil, in Santa Monica, Calif. on Friday, Oct. 16, 2009. (AP Photo/Matt Sayles)
Actress Ali Larter attends the Cinema Society premiere of "Obsessed", in New York, on Thursday, April 23, 2009. (AP Photo/Peter Kramer)
Actress Ali Larter poses on the press line at the "Heroes: Countdown to the Premiere" event in Los Angeles on Sunday, Sept. 7, 2008. (AP Photo/Dan Steinberg)
Ali Larter arrives at a party thrown by Nakheel and the Trump Organization to introduce The Trump International Hotel & Tower Dubai, Saturday, Aug. 23, 2008, in Los Angeles. (AP Photo/Chris Pizzello)
"It's a girl!" Later wrote under a photo of her super cute baby girl.
"We couldn't be more excited to share news of the arrival of Vivienne Margaret MacArthur," Larter's caption reads. "She came bearing gifts for her brother: Batman sheets and lots of Gummy Bears!!! 7.5 lbs of love."