The campaign runs on and offline with the aim of encouraging supporters to show their commitment to upholding children's rights.
It focuses on the plight of millions of children who are forced to live and work on the street, and is built around the strapline 'promise me'.
The campaign features press ads with headlines such as 'Promise me I won't be sold for sex' and 'Promise me we won't be forced to work 20 hours a day'.
The ads end with Unicef's pledge 'We promise. Will you?'
Unicef ambassadors actor Ralph Fiennes and author and journalist Martin Bell will support the campaign with personal messages to appear on Facebook and YouTube.
David Bull, executive director of Unicef UK, said: "Right now, the widespread denial of children's fundamental rights is being worsened by the impact of the economic crisis, the effects of climate change and the devastating impact of HIV and Aids.
"The result is that millions of children are at risk, struggling to survive on a daily basis without access to food, water, an education, or a safe place to live."
The online campaign starts today and the press ads and inserts will run from July 1. Inserts will run in titles including The Guardian, Radio Times and the Sunday Times Magazine while press ads will appear in the Telegraph, Independent, Guardian and Times.
