Murder Mystery - which was shot in Milan, Italy - also stars British actress Gemma Arterton, Luke Evans, John Kani and Terence Stamp.
While on location, Jen and Adam reportedly spent time with their friends George and Amal Clooney who live in the northern Italian resort region of Lake Como with their twins, Ella and Alexander.
The Murder Mystery premiere comes as reports claim Jen is about release a tell all memoir, inspired by her good friend Demi Moore.
Last week, Radar Online reported that Jennifer is planning to pen a book about her life and love, including her failed romances with Brad Pitt and ex-husband Justin Theroux.
Jen and Brad, who were married from 2000 until 2005, ended their union after Brad fell in love with his co-star Angelina Jolie on the set of Mr and Mrs Smith.
The exes shocked the world when Brad was spotted quietly arriving at Jen's star-studded birthday party on LA's Sunset Boulevard in February.
Brad's appearance confirmed more than a decade of rumours that the pair remained close friends following the break down of their marriage.
Other famous faces at the upscale event included Jen's former Friends co-stars Courteney Cox and Lisa Kudrow, as well as industry heavyweights Kate Hudson, Reese Witherspoon, Robert Downey Jr, the Clooneys and Ellen DeGeneres.