According to various Instagram posts from the nuptials, Erin stunned in a Danielle Frankel silk gown with sheer sleeves and a long veil for the ceremony, while her groom sported a white tuxedo jacket, black pants, and a bow tie by Todd Snyder.
Some A-list guests contributed to the event, with Erin's stepmom, Katharine McPhee, performing a song, Kate Hudson wowing the crowd by singing "Shallow" from A Star Is Born, and Jonah Hill taking a turn behind the bar.
Simon had something special planned for his bride as well, shocking Erin with a choreographed dance. After starting the performance solo, the groomsmen joined in before other guests, including Erin's sister, Sara, jumped on the dance floor to complete the flash mob.
As is tradition, the groom removed his bride's garter, but he added his own spin by fully sticking his head under Erin's dress to do the job.
The newlyweds also excitedly fed each other cake, before the night concluded with a fireworks display.
Following the happy day, Erin took to Instagram to share pics from the event, writing, "I got to marry the love of my life, and hopefully will never have to look at a seating chart again for as long as I shall live."