It happened in the Finaghy Road North area on Wednesday afternoon.
A paramedic was punched in the chest and face and his female colleague was badly shaken.
They are both now on sick leave and the ambulance is off the road for repairs. A 17-year-old who had requested the ambulance was arrested.
John McPoland from the NIAS said: “Any attacks on ambulance personnel are unacceptable and have a lasting impact on our personnel who are victims, when in fact they are simply trying to be carers.
“All these types of incidents impact on the ambulance service’s ability to respond due to a reduction in staffing and vehicles resources.”
Police said a youth was arrested on suspicion of assault occasioning actual bodily harm and criminal damage, and was later released on bail.