There were more than 300 entries from around the world in this year's event. This clever depiction of an elephant against the blue background of the UN flag was created by Patrick George from the UK.
Another winner came from Yang Lijie from China with this image of an elephant made from handprints - the theme of the competition this year was "the future of wildlife is in our hands".
The third winner (below) was Nabil Mendjeli from Algeria with a strong image again highlighting the challenges faced by elephants from the illegal trade in ivory.
According to the CITES secretary general John Scanlon, the overall quality of the entries was inspirational.
"The World Wildlife Day poster competition has helped to raise awareness about wildlife conservation, particularly the challenges facing elephants, in a very creative way. People from right across the globe have used their artistic talents to graphically express their support for wildlife, which is a great inspiration to all of us."
There were ten other finalists including this image from Victor Otieno from Kenya, again on the theme of how irreplaceable elephants really are.
Another interesting aspect was the large number of entries from children, according to one of the judges, Livia Firth, director of Eco-Age.
"It was so much fun to be a judge on this wonderful competition. We had an incredible amount of entries - from all ages and backgrounds and countries. I was so happy to see so many children also to submit - they are the ones we need to think about when we are depleting the earth resources at such a pace."
The  above image was created by eight-year-old Farzona Majidiy from Uzbekistan while the one below came from 12-year-old Raima Gupta from India.
The competition has been sponsored this year by the South African government who are hosting a key CITES meeting in Johannesburg in September called COP17. The winners are being provided with return air tickets to the event.
All this year's entries can be found here, while finalists can be seen here.
This is one of the three winning images from the UN's World Wildlife Day poster competition organised by the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES).