Bassac, a membership body for community organisations, and the DTA, a network of community practitioners, both held extraordinary general meetings last Thursday and said they received overwhelming mandates to create a new organisation.
The pair already have similar interests in community enterprise and community ownership of assets, have several members in common and are based in the same building.
The new, combined organisation will start operating in April next year.
"Together we will have an even stronger voice to champion the work of front-line community organisations," said Steve Wyler, director of the DTA.
"The overwhelming support for the merger highlights the value that our combined networks will bring to the community sector as a whole."
Both organisations said they were unable to comment further on the structure of the new organisation, whether there would be any job losses or who would take on the role of chief executive.