The Clondalkin Detective and Drugs Units performed a planned search at a premises located at the Bluebell Industrial Estate last Tuesday.
The operation yielded 32.5kg of suspected heroin and half a kilo of suspected cocaine. The haul has an estimated street value of €5m.
A handgun and some ammunition were also seized.
A 39-year-old man was arrested last Monday in connection with the incident, and remains in Garda custody.