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:

Kildare Tenant Awarded €23,000 After Landlords Refused HAP Scheme
Asylum Seekers Still Allowed Enter Ireland Without Passports Or Documents, Officials Tell Kildare TD
Former Well-Known GAA Referee From Old Kilcullen Told He Faces Prison For Abuse Of Niece
Locals Urged To Make Their Votes Count In Tomorrow's Presidential Election
Land Owner To Decide If Details Will Be Released On Hundreds Of Skeletons Found In Naas
€10 Million Settlement For Celbridge Man With Cerebral Palsy In National Maternity Hospital Case
Clicks And Cash: Kildare TD Mark Wall Among Top Social Media Spenders During Last General Election
Kildare Cllr Tom McDonnell Aims Blame At Gardai, Saying He Was "In the Front Line" During Citywest Riots