The figure compares to €9.9M spent in 2020.
The HSE spent €13.6 million 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, €9.9 million was spent on private ambulance services by HSE hospitals - rising to just under €13.6 million last year.
Lifeline Ambulance Service got €4.3 million in 2021 - the highest amount.
The HSE says the big difference in expenditure between 2020 and 2021 was down to Covid-19.
It also said private providers helped with testing and vaccination.
David Hall is its chief executive - he says private providers are needed: