The UK will lead a global steering group to dispel the myths that rhino horn can cure cancer or help with strokes, which are fuelling demand for it in Asia so much that it is now worth £50,000 a kilo.
Countries and conservation groups across the world will also work together by sharing intelligence, policing tactics and public awareness campaigns against the illegal trade.
The agreement was reached at the Convention for International Trade in Endangered Species in Geneva.
Environment Secretary Caroline Spelman said: “Criminals trading in rhino horn have lined their pockets while bringing this magnificent animal to the brink of extinction, but their days are now numbered.
“We will be leading global action to clamp down on this cruel and archaic trade, and to dispel the myths peddled to vulnerable people that drive demand.”