Girls from Llanrwst recorded the message in Brussels
The Urdd Gobaith Cymru issued its message of goodwill from Brussels on Saturday in its 80th anniversary year.
The 50,000-strong organisation helps young people to maturity through use of the Welsh language.
The organisation has broadcast a message of international unity and citizenship via radio since 1922.
Four pupils from Ysgol Dyffryn Conwy in Llanrwst, north Wales, were chosen to make this year's broadcast in 18 different languages, including Welsh.
The Urdd said the latest missive was particularly important following 11 September and the ensuing conflicts in Afghanistan and around the globe.
And the plea for harmony and understanding on the organiastion's 'Goodwill Day' is also published in eight languages on its website.
India question
Working with the Christian Aid charity, the movement is using the message to raise Welsh awareness of youth poverty at Calcutta, India.
And Jill Evans - one of Wales' members of the European Parliament - is also distributing the message to all 626 MEPs.
"Fostering international understanding is one of the bedrocks of the European Union," she said.
"I hope that, by sending this message, we will be able to bring all our nations closer together in a spirit of peace and goodwill.
"Having just returned from Palestine - where I saw graphic examples of suffering at the hands of violence, injustice and poverty - I think it's more important than ever for Welsh youth to be aware of why we need to create a fairer world."
The Urdd's first message - a prayer for peace - was sent by the Reverend Gwilym Davies from the Rhymney valley, south Wales.
He was a pacifist who helped found the Welsh Union of the United Nations and later UNESCO.
It was not transmitted by the BBC World Service until 1924 after being picked up by the corporation using morse code.
When Rev Davies died in 1955, the Urdd movement vowed to continue his work, ensuring a similar message was sent all over the world.
Today, the sentiments are sent via post, radio and the internet.
The Urdd's annual eisteddfod is held at Cardiff in June.