Homeowners with variable mortgages at AIB and EBS are going to have to pay more for their repayments.
A rate hike announced in March comes into effect today.
Mortgages at AIB will go up by 0.4% - while those at EBS will go up by 0.25%.
The hikes come despite the ECB rate falling to a record low of 0.5%.
Other lenders have also failed to pass on last month's ECB reduction to customers on variables.