The discovery was made following the search of a house in Edenderry.
Gardaí in Offaly have seized €320,000 worth of cannabis.
Three men aged in their 20s, 30s and 40s have been arrested during the course of the operation in Edenderry.
Police estimate around 400 fully mature cannabis plants were discovered during the search of a house, which will now be sent for analysis.
The search took place following the search of a house in Drogheda by the Louth Divisional Drugs Unit earlier today.
Investigations remain ongoing.
Just hours later another major seizure worth €2.1m has been made in Laois.