"I call it the gastronomy of liberation," said Carlo Petrini, the founder of the Italy-based movement, holding up an African recipe booklet as a first example of collaboration between the two.
Petrini said Africa had seen "gastronomic colonialism" in which local cooking was spurned in favour of British, French or Italian cuisines.
"There will be pleasant surprises in the years to come. There will be more local chefs who will be proud of their indigenous cuisine," Petrini said.
The three-year agreement will see the Food and Agriculture Organisation (FAO) and Slow Food carry out joint campaigns to highlight neglected food crops, promote local culinary traditions and help train agronomists to work on small family farms.
FAO director general Jose Graziano da Silva said promoting local production and consumption would help reduce the recent volatility seen in food prices, because fewer products would enter the international food distribution system.
"Small farming can be part of the solution to global food insecurity," he said at a joint press conference with Petrini at the foreign press club in Rome after the signature of the agreement.
Petrini, whose movement has attracted thousands of foodie followers in developed countries and helps promote sustainable farming in the developing world, said the deal with FAO came at a "historically important time" for the food industry.
"We have lost our way. We have closed ourselves up in (television cookery show) 'Masterchef' and other self-referential formats," he said, adding: "Gastronomy is not just about beautiful food."