The 15-year-old was taken into custody after testing positive for cannabis while behind the wheel.
Gardai stopped the car after observing the young teen driving near Dublin Castle.
A garda tweet said: “DMR Roads Policing, Dublin Castle, observed car being driven by 15-year-old youth who subsequently failed roadside drug test.
“Arrested on suspicion of driving under the influence of cannabis, blood specimen taken. Investigations are continuing.”
Meanwhile, a motorist in Carlow disqualified from driving for six years tested positive for two drugs – after being nabbed for speeding.
A roadside breath test found opiates and cannabis in the driver’s system.
This was after gardai stopped the motorist for travelling at 154km/h on the M9.
A garda tweet said: “Carlow Roads Policing Unit stopped a driver speeding at 154kph on the M9 motorway.
“The driver, who was already disqualified for 6 years, tested positive for drug driving following a roadside drugs test.
“Driver was arrested and charged. Court proceedings to follow.”