The pair have reportedly decamped to Italy with their closest family and friends who will witness them saying "I do" in a romantic ceremony.
Pictures have emerged said to be that of Jess and Justin's wedding party who were treated to a trip to local tourist attractions on Wednesday and a spectacle of traditional Italian life.
And an impressive burst of fireworks illuminated the night sky as the celebrations got into full swing.
Us Weekly reports that Justin's music manager Johnny Wright is also in attendance and joined the gang for dinner and cocktails at a beachfront location which was decorated with lanterns and serenaded with songs like Marvin Gaye's "Let's Get It On."
Guests were out again on Thursday to the beautiful Italian countryside for an intimate lunch where platters of fresh food and local fare were laid out.
So far, Jessica's Seventh Heaven co-star Beverly Mitchell and Andy Samberg have been some of the celebs seen among the guests who were flown out for the big event.