The music concert, hosted by celebrity blogger Perez Hilton, will take place at London's Electric Brixton on July 13.
Cher Lloyd was confirmed as the show's first act last week, with 100% of the ticket sales going towards the BRIT Trust which provides music education for young people.
Faith is expected to perform songs from her latest album Fall To Grace, while McElderry will sing a number of hits from his studio albums Wide Awake and Classic.
Meanwhile, Perez Hilton recently told Digital Spy that he predicts One Direction will split up within the next few years.
Tickets for Perez Hilton's One Night In London are on sale now.
Watch the music video for Paloma Faith's '30 Minute Love Affair' below: