However, as guests entered the Los Angeles Theatre, reports emerged that the "engagement party" was actually a secret wedding - especially after Gwyn's celeb mum Blythe Danner was spotted entering the venue with a Monique Lhuillier bridal dress bag.
She later posted an adorable snap of herself posing with her husband-to-be, 47, alongside the caption: "Thank you #ryanmurphy for the most incredible evening to celebrate our love".
Gwyneth and Brad previously confirmed their engagement in a sweet message earlier this year.
The Vogue cover girl was previously Wednesday to Coldplay singer Chris Martin, with whom she has two children - Apple and Moses.More news: Southampton 2 Chelsea 3: Two-goal substitute Giroud inspires turnaround
"It felt intimate and very special".
'There will never be adequate words to express our gratitude.
She said: "I've never had a wedding before". We feel like the luckiest people on the planet because we have you in our lives.
'And most of all thank you @bradfalchuk for the true happiness, ' added the Emma star. (Photo Maya Meyers photography)'.More news: Foster will not participate in 49ers team activities
Gwyneth and Brad invited 400 of their closest friends to the engagement-turned-secret-wedding bash, and in terms of A-list attendees, it looks like they've even given Prince Harry and Meghan Markle a run for their money.More news: Commonwealth Games organizers under fire for closing ceremony