Created by Abbott Mead Vickers BBDO, "London needs you alive" is aimed at 13- to 16-year-olds and involves grime and rap stars, poets, bloggers and photographers, alongside the mayor of London Sadiq Khan.
A film, running on social media, features kids from schools across London sharing their message to the camera.
The campaign was created by Esrael Alem, Dan Warner, Filmawi Efrem and Andy Vasey. The film was directed by Novemba through Academy Films. The media agency for the campaign is MEC.
For the stills used in the campaign, AMV BBDO worked with photographer Tom Sloan, who mentored two young photographers sourced by Brixton charity Photofusion. The images will be used on Instagram and on poster sites around the city.
Alex Grieve and Adrian Rossi, executive creative directors at AMV BBDO, said: "Tackling knife crime is one of the toughest briefs in London. Our best chance of success is to do something radical. We got rid of the guts and gore you’d expect from a knife crime campaign, along with most of the usual advertising media channels and gave kids something that would really resonate.
"London Needs You Alive is a movement designed to be owned by Londoners. It can be shared just as easily by influencers like grime artist Bossman Birdie and poets like Hussain Manawer or The Mayor of London as it is by the thousands of young Londoners affected by knife crime in their daily lives."
Khan added: "Too many of our young people are being senselessly lost to knife crime, and it has to stop. Our young Londoners are too valuable to risk their lives by carrying a knife. They are our future musicians, artists, sportsmen and women, comedians, scientists, politicians, entrepreneurs and role models. We need them."