Hers was the third instance of the rare blood clots appearing in people who have been administered the vaccine in Australia. The other two are recovering well, the Therapeutic Goods Administration (TGA) added.
It said it was "carefully reviewing" similar instances in Australia.
The New South Wales woman received the AstraZeneca vaccine on April 8, the day that the government announced that the Pfizer vaccine would be given as a preference to patients under 50, delaying its inoculation timetable.
In the absence of an alternative cause for the clot that she developed, Australia's Vaccine Safety Investigation Group (VSIG) "believed that a causative link to vaccination should be assumed at this time," the TGA said.
The VSIG had held a meeting late on Friday following news of the woman's death.