Fellow actor Paul Mescal quickly helped her up the stairs.
While accepting her award for Female Actor in a Television Movie or Limited Series for her work in George & Tammy, Chastain tripped while going up the stairs to the stage. Chastain made a quick recovery, though, and was helped up the steps by Paul Mescal and a few other strapping gentlemen.
ET's Denny Directo spoke to Chastain about the moment just minutes after she won her award, where she brushed off the fall.
"I am the one who never expects this is going to happen," Chastain said of her big win. "Yeah, I fell on the stairs, that's good because some people didn't know that I did."
Chastain, who stunned in an off-the-should fuchsia gown, said it was her dress to blame for the accident. "I was trapped in my dress and I had very nice men helping me, so that was a plus."
Calling the category "stacked," Chastain first thanked her fellow nominees, which included Niecy Nash (Dahmer – Monster: The Jeffrey Dahmer Story), Amanda Seyfried (The Dropout), Emily Blunt (The English) and Julia Garner (Inventing Anna), and ended it with some words of encouragement for aspiring actors.
"So, I just want to tell everyone who might be struggling at home, to all the actors that I get to meet, keep going, you're one job away," Chastain said. "I look forward to working with you. I'll see you on set, and I love you. Thank you so much."
The 29th annual Screen Actors Guild Awards took place at the Fairmont Century Plaza in Century City, California, and streamed live on Netflix's YouTube channel. Stay tuned to ETonline.com for complete SAG Awards coverage and the full list of winners.