The HSE spent €13.6m euro on private ambulance services last year.
According to freedom of information figures, it's a 37% increase on the previous year.
The HSE's National Ambulance Service mainly deals with emergency calls.
Private ambulance are mainly used by hospital groups to transport patients who are less seriously ill.
In 2020, €9.9m was spent on private ambulance services by HSE hospitals - rising to just under €13.6m last year.
Lifeline Ambulance Service got €4.3m in 2021 - the highest amount.
The HSE says the big difference in expenditure between 2020 and 2021 was down to Covid-19 - it says private providers helped with testing and vaccination.
