Jessica, 34, stunned in a floor length white lace dress, which matched Ashlee's dress of the same material and colour.
Looking even more adorable though, was Jessica's two-year-old daughter Maxwell, who was flower girl for the big day.
Sharing a beautiful snap of her and Maxwell at the wedding, Jessica wrote: "Bridesmaid and flower girl for @ahsleesimpsonofficial and @eross88. I am madly in love with this moment!"
Meanwhile Evan's mother Diana Ross has gushed about her son's big day.
The 70-year-old superstar told Yahoo: "We had a beautiful rainbow surrounding us, loving family and friends, great music, great speeches from caring friends, and joyful children dancing the night away.
JESSICA SIMPSON UNVEILS TONED FIGURE IN SWIMSUIT SNAPS
"Wishing Evan and Ashlee congratulations. I want only love, happiness, and joy for my son and his bride."
Diana even performed her song Endless Love for the new couple – sounds like the day was perfect.