The couple, who are also preparing to tie the knot later this year, jetted to New Orleans, Louisiana, to watch the 'How To Make It In America' star marry tattoo artist Scott Campbell.
A source told UsMagazine.com that other pals including Lake's 'What Happens In Vegas' co-star Cameron Diaz, Eva Longoria, Josh Hartnett, Kate Bosworth and Alicia Silverstone also flew in from Los Angeles to attend the nuptials.
The ceremony took place at the Marigny Opera House, which features 40 foot high arched ceilings, stained glass windows, and mottled plaster walls.
Guests cheered as the 34-year-old actress and her beau, who got engaged in March 2012, exchanged vows before riding off to their reception together on a motorcycle.
A source said: ''Lake wore a white tiered dress, sleeveless with a high beaded neck and V-cut back. She was wearing a veil and carrying a crimson red rose bouquet.''
Their celebrity guests have been making the most of their trip to New Orleans by taking in the local sites.
Several were also spotted enjoying a Swamp Tour in the nearby Bayou Lafitte on Friday (31.05.13), where they fed marshmallows to alligators.