Violence against ambulance staff increased more over the last year than in any of the previous six.
According to figures obtained by BBC Wales, there were 273 reported assaults on Welsh Ambulance Service staff last year, up by 14 per cent on 2014-15, and higher than any year since 2009.
Incidents include physical violence and verbal abuse.
Tracy Myhill, chief executive of the Welsh Ambulance Service, said: "Our staff should be able to work without fear of violence, abuse or harassment.
"They're there to help the community's emergency medical needs and do not need to be obstructed by unwarranted attacks in already difficult circumstances.
"That's why it's so disappointing to see an increase in the number of attacks."
Darron Dupre, ambulance lead for Unison Cymru Wales, added: "It is both terrible and an indictment of how little we value emergency crews that reported assaults in Wales have increased by over 50 per cent since 2009-10.
"These figures also show that assaults are not just carried out by patients who are under the influence, or who do not have the mental capacity to understand their behaviour.
"They are carried out by patients' families, friends and abusive crowds."
David Thomson, who has been a paramedic for 23 years, mostly in north Wales said he was assaulted three years ago.
He said he was confronted by a man demanding he move his car, when responding to an emergency call.
He added: "He was standing there, aggressively, and then he went for me. He said 'I'm going to kill you' and threatened my family.
"He took the drugs from my vehicle, which I managed to wrestle back, but then got into his car and tried to ram into mine. Then he drove away."
Later that day, the man arrived at the ambulance station where Mr Thomson was working. "He came there with the intention of assaulting me", he said.
"It was just completely and utterly vicious. I had to take time off because I was so shaken."