Melinda Freeman, 26, was found dead by her husband Craig at her home in Whittlesea in October 1991, after she was assaulted.
Police remain confident the case can be solved despite three decades having passed, and are calling for anyone with fresh information on Mrs Freeman or her husband's movements on the day of her death.
On October 4, 1991, Mrs Freeman and her husband spent the day with immediate family to celebrate her sister's return from overseas.
The couple returned to their home on Yea Road about 4pm.
Later, Mr Freeman left the house and took their nine-month-old son to a card game to give his wife time to study for her beauty course.
When they returned at 11.30pm, the house looked like it had been ransacked and the front door was open.
Mr Freeman found his wife's body lying on the landing on the top storey of the house.
Victoria Police Homicide Squad Detective Inspector Dean Thomas on Wednesday said hundreds of people had been spoke to over the murder and confirmed Mr Freeman remained a person of interest.
"We certainly do have some persons of interest that remain to this day," he told reporters.
"It's fair to say that the former husband remains a person of interest in this investigation.
"But we have to keep an open mind to that, and be very open to the fact that it may be some other person or persons involved in this."
Det Insp Thomas said he hopes the $1 million reward will encourage people who may have information to come forward.
"In 2018, we did receive anonymous information from a member of the community," he said.
"We're appealing to that person to please come forward again. We are keen to continue speaking to that individual."
He said Mrs Freeman's family was "very pleased" about the reward and hopeful it could lead to the case being solved.
"We very much owe it to Melinda's son and also her family to be able to answer the questions that they have," he said.
"We've got to remember that a nine-month-old son has grown up without his mother and I have no doubt he thinks about this on a daily basis."
Six years after the murder, in 1997 a coroner delivered an open finding during an inquest into Mrs Freeman's death.
Coroner Jacinta Heffey said she was unable to support arguments by Mrs Freeman's family that she was killed by her husband.
The inquest was told that Mr Freeman was having an affair before his wife's death.
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