Members of the family, including a teenager, were in the house near the village of Rathmore when gardaí with a search warrant entered it at about 11pm on Thursday.
Inside the house, members of the Kanturk drugs squad recovered a small quantity of cannabis.
They then searched sheds close by where they found 240 plants valued at €160,000. They also seized a kilo of processed cannabis worth about €10,000.
A Garda spokesman said that growing paraphernalia including heaters and watering equipment was also found in the sheds.
“We would describe the set up as an elaborate growhouse,” he said.
The scene was examined yesterday by garda forensic experts.
The spokesman said that no arrests had yet been made and inquiries were still ongoing.
The plants will be sent for analysis to Garda headquarters in Dublin after which they will all be destroyed.
It is the largest grow house ever discovered in the Kanturk Garda District, which covers most of North-West Cork and a small part of Co Kerry in the Rathmore area.
Members of the Kanturk drugs unit, aided by detectives from Mallow, seized about €250,000 worth of cannabis resin in the Liscarroll area two years ago, while last year they discovered €30,000 worth of growhouse plants in Millstreet.