The Welsh Ambulance Trust said it has hit its target for response times for the first time in two years.
This month GPs were drafted in to control centres to help assess calls
Figures so far for March show the service is reaching 60.8% of emergency calls within eight minutes.
It beats the 60% target set by the Welsh Assembly Government.
It follows a difficult period for the service, which last month asked people living in Cardiff and the Vale of Glamorgan to only dial 999 in a life-threatening emergency.
The service said it had beaten the target to far this month and was on track to maintain that level.
Official quarterly figures will be released in May.
The figure for March, traditionally one of the most difficult months for the service, compares to 49.8% a month earlier.
Director of ambulance services Mike Cassidy has praised staff for their commitment to meeting the "very challenging" target.
"They have worked magnificently to make this happen, especially after a February when adverse weather conditions and problems with ambulances queuing at hospitals caused the system to crash," he said.
The service has been thrust into crisis over the last 12 months, with changes at the top and a public inquiry ordered by assembly members into failings.
New chief executive Alan Murray took over last August, when the figure for calls reached in eight minutes was 55.4%.
A series of measures, designed to bring improvements have since been brought in.
These include using GPs in control centres, more use of rapid response vehicles and "dynamic deployment" - where the service predicts where demand for ambulances is going to be, according to Mr Cassidy.
He added: "We mustn't rest on our laurels and must make the changes in work practice the new norm and for that we depend on the professionalism and flexibility of our staff to work with us to drive even more effective strategies for improving response times."