The study acknowledges that some jobs would inevitably be lost by switching to a "greener" economy as older technologies give way to the new.
But the heads of the U.N.'s International Labor Organization and the U.N. Environment Program emphasized that net gains of 0.5 percent to 2 percent in total global employment are possible, mainly through more renewable and efficient energy use.
ILO Director-General Juan Somavia and UNEP Director Achim Steiner said they hope international policymakers at the Rio+20 conference in Brazil keep this in mind.
Most of the net employment gains are expected in agriculture, forestry, fishing, energy, manufacturing, recycling, building and transportation, and some 1.5 billion people -- at least half of the global workforce -- are seen as being affected by the transition.
In the European Union, the study says, already nearly 15 million people work in jobs that either directly or indirectly help protect biological diversity and rehabilitate natural resources and forests.
The upcoming summit is more about prodding countries into action than persuading leaders to sign binding agreements.
Negotiators hope to produce a final statement for the June 20-22 conference, and some developing nations are worried that emphasizing environmental protections could hinder their economic development.
But the U.N. agency heads said that is a false dichotomy, as shown by the study.
"We don't have to choose between protecting the environment and creating jobs," Somavia said.