Officers from the Garda National Drugs and Organised Crime Bureau (GNDOCB) stopped the van on the M7 in the Kildare area at 6:30am.
A substantial amount of cash was located and seized, estimated to be in excess of €1,000,000 - subject to conclusion of counting.
A number of follow up searches were undertaken in the midlands and an additional sum of cash, estimated to be approximately €10,000, was recovered.
The search was carried out as part of ongoing investigations targeting persons suspected to be involved in organised crime.
A man (45) was arrested and is currently detained, pursuant to the provisions of section 50 of Criminal Justice Act, 2007, at Portlaoise Garda station.
Gardai say he was arrested on suspicion of involvement in participating in the activities of a criminal organisation, to facilitate money laundering, relating to the suspected proceeds of drug trafficking, pursuant to the provisions of section 72 of Criminal Justice Act, 1996.
Speaking today Assistant Commissioner John O’Driscoll, head of Organised and Serious Crime, said: "An Garda Síochána continues to pursue organised crime groups who are believed to involved in supplying illicit drugs within our communities, the motivation for which is financial gain.
"We again today have made a significant advance in our attempt to dismantle organised crime groups, by locating and seizing the suspected proceeds of their criminal activity.
"Despite our significant commitment to tackling issues associated with the COVID-19 pandemic, at this time, An Garda Síochána remains focused on protecting communities from serious and organised crime, including cyber enabled crime, drug trafficking and associated money laundering.”
The investigation is ongoing.