It comes as a survey reveals more than a quarter of Irish people haven't attended confession in a decade or more.
Almost 80 per cent said they do not go at least once a month.
The 12m high structure allows cars to drive through an 'express lane to eternal salvation'.
A spokesman said: "Ireland has changed a lot since the last Pope's visit - gay marriage is legal, we've repealed the Eighth Amendment, and even secretly cheered for England in the World Cup.
"With decades worth of sins clocked up since then, we're providing a convenient means to complete your contrition with your keys still in the ignition.
"And if the Catholic hierarchy have anything they'd like to get off their chests too, they are more than welcome to take a spin through our mega drive-thru confession box while they're here."
The publicity stunt comes as 500,000 are expected to gather this weekend for a Mass in Dublin's Phoenix Park.
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