Mortgage customers are being urged to "not to be distracted by the lure of cash" when considering their options.
The Competition and Consumer Protection Commission (CCPC) is launching a new campaign to advise customers they could save hundreds of euro a year.
It says that while many lenders are now offering special offers such as cashback, customers should focus on the potential long-term savings that can be made through lower rates.
The CCPC says that a customer with €250,000 left to pay over 25 years could save tens of thousands of euro over the course of the mortgage by looking at the options available.
Áine Carroll of the CCPC explained: "Immediate cash is hard to say no to, but offers like these also make it harder for consumers to compare one product against another.
"A contribution to your legal or valuation fees may appear to save you money in the short-term, but the impact of an even slightly higher rate will be significant in the long-term."
She added: "If you are weighing up your mortgage options, park the special offer and look at the rate you will be paying as well as any terms and conditions attached to it."
It comes as AIB announced it is dropping its variable rates by 0.25%, which the bank says will mean annual savings of more than €300 on a €200,000 mortgage.
AIB claims that more than 100,000 customers will benefit.
Several of Ireland's main lenders have cut their mortgage rates over the last year, and the latest change is expected to put pressure on other lenders to follow suit.