Robbie Keane sealed the deserved win on Saturday just before halftime, ending a fine 40-metre run with a powerful, deflected shot from just outside the box.
The Dutch disappointed in their last warm-up before Portugal, proving harmless up front. Their best chance came 15 minutes from time but Shay Given brilliantly saved a Roy Makaay header.
The Irish had gone close to an opening goal after only three minutes when Keane intercepted a header away by Giovanni van Bronckhorst but his shot narrowly missed the target.
Ten minutes later the Dutch had their first chance but Patrick Kluivert failed to cash in.
On 20 minutes the impressive Keane was unlucky with a bicycle kick that struck the crossbar.
After the break Dutch coach Dick Advocaat paired Rafael van der Vaart with Ruud van Nistelrooy while Clarence Seedorf replaced the totally out of form Kluivert.
Ireland might have gone further ahead in the first seven minutes of the second half. A Clinton Morrison volley went just over the bar and goalkeeper Edwin Van der Sar foiled a breakaway by Keane.
The Dutch pressurised the Irish defence but kept searching for the solution through the centre. Despite the presence of wingers like Arjen Robben and Andy van der Meyde the flanks were hardly used.
To add to their concerns Seedorf was forced off the pitch after only 18 minutes with a suspected pulled muscle.
The Netherlands' other opponents in Group D at Euro 2004 are the Czech Republic and Latvia.
Advocaat said: "We played a very poor match and it was clear that my team performed not as they were supposed to do."
"It didn't work out with Kluivert and van Nistelrooy but that is also to do with my midfielders who all gathered on a small area so we hardly had any space to create chances."
He added: "Seedorf will have an MRI scan tomorrow. He felt something in his hamstring."
