Speaking to Bloomberg, the investor who coined the term "emerging markets" in 1981 said gains in such countries will be limited by the effects of Europe's sovereign debt crisis on exports and monetary policy.
The Dutchman predicted a slowdown over the next three quarters, but said the economies of many developing nations are now too established to suffer significant damage caused by fiscal problems in Europe.
"In emerging markets, we are already past the worst point of this year," Mr Van Agtmael told the news provider.
"Don't forget, emerging markets are now a third of the global economy and rising to 40, 50 per cent by the end of this decade."
A former World Bank official and fund manager, Van Agtmael is now the chairman and chief investment officer of Emerging Markets Management.
By Asim Shah