Ali Wentworth & George Stephanopoulos' Daughter Elliott, 18, Heads to Prom in Elegant Black Gown

It's prom night in Ali Wentworth and George Stephanopoulos' household.

On Wednesday, Wentworth, 56, shared a photo of her 18-year-old daughter Elliott Anastasia wearing an elegant black gown as she posed next to Stephanopoulos, 60, ahead of the big school fête.

"Prom night!" the actress wrote in the caption — teasing, "that is not her date...."

Earlier in the day, Wentworth spoke about preparing for her daughter's big milestone moment while guest-hosting Live with Kelly and Ryan.

According to the mother of two, who also shares 16-year-old daughter Harper Andrea with Stephanopoulos, picking out Elliott's dress was the biggest struggle.

"The prom dress, I have to basically remind my daughter that it's not the Met Ball or her wedding," she told host Ryan Seacrest. "The dress has to be under $100 and you also can't dress like a lady of the night, you know what I mean? I don't mean like a turtleneck sweater dress, but something in between."

"We've gone through a lot of dresses and I think they love the ritual of it, because we went to all these department stores like Bloomingdales and tried on all these dresses. I was like, 'This is a waste of time,' " Wentworth continued.

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The comedian went on to say that the ceremony surrounding prom was fun for her daughter.

"I did hair and makeup this morning for the show … and my hair and makeup person is staying at my house all day. She's going to get Elliot 'in the works' started at 3 p.m. for a 6 p.m. prom!" she explained. "It's a big deal."

One thing that wasn't a big deal though? Elliot's date, who passed with flying colors in Wentworth's eyes.

"I approve of the date," she said.

For Wentworth, Elliott's big night is also a special one for the family as both she and Stephanopoulos did not go to their proms when they were teens.

"George did not go to prom because he had chess club that night," Wentworth revealed, joking that the Good Morning America anchor — whom she married in 2001 — is "the nerdiest thing you've ever seen."

"I went to an all-girls school, so we didn't have a prom. So this is like our first prom," she explained, jokingly adding, "I said to my daughter Elliott, 'I'm also going to wear a gown.' "