Police found the body of Dr Preethi Reddy (32), in a suitcase in her vehicle.
Reddy was last seen waiting in line at McDonald's in George Street on Sunday, the police said.
But it's thought he stuffed her body into a suitcase, loaded her into her vehicle and dumped the VW Golf in Kingsford near the University of NSW.
Investigators found Preethi Reddy dead in her own vehicle on Strachan Lane in Kingsford about 9.30pm on Tuesday, having been stabbed "numerous times".
32-year-old Reddy had been attending a dental convention in St Leonards over the weekend where he spent Sunday night in a hotel on Market street with her ex-boyfriend, Harshwardhan Narde.
Police have since discovered the man died in a "deliberate" head-on collision on the New England Highway at Willow Tree, in the Upper Hunte on Monday.
The police said they spoke to Narde, aged in his thirties, as part of the missing persons investigation, before his death.
Police will say Reddy and her former boyfriend "met up in Sydney but we are now looking at all movements between those two to establish what happened", Detective Superintendent Gavin Dengate told reporters on Wednesday.
Preethi Reddy was last seen waiting in line at McDonald's in George Street on Sunday
The body had numerous stab injuries.
Detectives are investigating the crash, which they believe was deliberate.
The ABC understands Dr Narde was the key suspect in Dr Reddy's murder.
Many are posting condolence messages on social media for Dr Reddy this morning.
Reddy told her family members she would have a late breakfast in the central business district before returning home.
Preethi's disappearance is "out of character" and there are serious concerns over her welfare, a New South Wales (NSW) Police spokeswoman said.
Investigators believe that Narde did not accept that, and had attended the weekend conference purely in order to see her.
Her remains were found last night in Strachan Lane, just a few hundred metres from Anzac Parade and about 700m from the University of New South Wales.
She worked as a general dentist at Glenbrook Dental Surgery in the lower Blue Mountains, and was previously employed at Hurstville Dental And Physio Centre in western Sydney, and Dapto Smile Dental Centre, near Wollongong. She has been missing since Sunday.