There were just under 4,500 complaints to the office of the Financial Services Ombudsman in 2014, a fall of 42% from the year before.
Almost half of these resulted in some form of redress for those customers with complaints against financial services companies.
The Ombudsman said that new powers given to the office last year - meaning the complaints upheld against individual financial services providers can be published - had a significant effect on complaint handling by the industry.
It said this means that more complaints are being dealt with at an earlier stage, and settled, and that this is a very positive outcome for the industry.
Danske Bank Group and credit card firm Avant Tarjeta, or Avant Card, had the most complaints substantiated and partly substantiated by the office.
The majority of complaints in 2014 were about investment products, but this sector also saw the biggest reduction in complaints, down by 65%.
Complaints about insurers fell by 49% and complaints against banks were 27% lower.
On a product basis, mortgages continue to be the highest driver of complaints, representing 28% of all complaints received.
The Ombudsman said mortgage issues remain a concern and more work needs to be done.
Compensation paid out last year rose by 2.4% to almost €950,000.