The 43-year-old woman fell as she tried to catch the postman in Llewellyn Avenue, Cardiff, just after 10:00 GMT on Saturday.
Neighbours waited with the woman and made repeated attempts to get an ambulance.
The Welsh Ambulance Service is investigating the cause of the delay.
Neighbour Jackie Whiller said: "They insisted we didn't move her, so we covered her in blankets.
"This went on for nearly five hours and we had rung them about six times.
"They did call back twice and at about 2pm they asked if they could send a taxi ambulance and we said lots of us here have cars but had been told not to move her. So he said to keep her there.
"She was shaking quite badly at one stage."
The woman was taken to hospital with a double leg break and remained there overnight.
Ms Whiller repeatedly tweeted the ambulance service as she was waiting for the ambulance to arrive, who apologised saying they appreciated it was a "distressing wait".
A spokesman for the Welsh Ambulance Service said: "We apologise to the patient and family for the stress caused and want them to contact us so we can speak to them directly."
The Welsh Ambulance Service has apologised after it was claimed a woman was left lying on the pavement for more than five hours with a broken leg.