The Print Young Lions have been tasked with creating a print ad campaign to raise awareness of the cancer information available from the charity and the support it can offer.
Hilary Cross, the director of external affairs at Macmillan, unveiled the challenge at the Cannes Festival yesterday.
She told Campaign: "The challenge we have given the Young Lions is to help us with our global profile in the English speaking world, because we already have an audience outside of the UK who find us relevant and engaging.
"30 per cent of our online community and 24 per cent of the millions who visit our website every year come from outside the UK.
"Currently, audiences primarily in the US, Canada and Australia may not know about us, or may have a limited view of us. But once they get to us they find support and help that is just what they need.
"Digital has made us a global brand and we need to start embracing that. The massive growth of digital and social media has broken down the barriers that confine brands to one geographical space.
"If someone in Australia Googles a type of cancer or if someone in the US wants to know how to tell their kids about their cancer or if someone in Canada wants to discuss the side effects of a particular drug, the help and support they can get through Macmillan is the same as that we develop for UK audiences."
With an annual budget of €190 million (£161.3 million), Macmillan's aim is to change the nature of cancer support.
The charity is also working with corporate partners to help expand its global reach, including a piloting a new face-to-face support service with Skype.
Cross is appealing to other global partners to providing services in the future, and hopes the print competition will help build momentum.
She said: "What I hope to achieve is to see some new, exciting and different ideas about how we can achieve cut through outside the UK with English speaking audiences, specifically a brand ad that I can take and actually use.
"I have no doubt of the amazing impact great advertising can have – Macmillan invests in building our brand, including using TV advertising, because it has significant impact on raising mass awareness and shifting people's perceptions about who we are.
"Our latest ‘not alone’ campaign, created by VCCP, is proof of that and has been our most successful ever. The power of TV and all advertising is not just about being out here [in Cannes] – it's also about resonance and relevance, about being memorable and moving, and stopping people in their tracks, speaking directly to them."