Argyll and Bute Council granted permission to Ardyne Estates to build the facility at Ardyne Point.
The council said the factory was expected to support 150 jobs, and add more than £7m to the local economy.
A masterplan identifying potential future developments in the wider Ardyne Point area was also approved.
Ardyne Estates has not indicated when construction work will start on the factory.
David Kinniburgh, chair of the council's planning committee, said: ''We wholeheartedly support this development.
"It will be a great boost to the economy of South Cowal in particular and Argyll and Bute in general.
"A particularly important feature is the masterplan which identifies potential future developments in the wider Ardyne Point area.
''The plan is flexible but includes areas for tourism, business, leisure, housing, marine and aquaculture developments.
"This site can now be developed in a sensible and sustainable way, benefiting both developers and the wider community."
Plans for a new £19m fish processing plant at a former oil rig fabrication yard in the Cowal Peninsula have been given the green light.