The man, now aged in his 80s, appeared in a Victorian County Court on Wednesday.

He pleaded guilty to two charges - indecent assault and gross indecency.

The victim was assaulted more than 30 years ago, when she was aged between four and five years old.

The court heard the victim would often visit her grandparents' Wimmera property during the school holidays.

On three occasions, the victim was laying on a bed next to her grandfather when he touched her inappropriately.

On another occasion, the man exposed himself to the victim and asked her to touch him.

The man told his granddaughter not to tell anyone about the incidents, as it was their "little secret".

The victim didn't tell her family about the abuse until 2017, when she also made a police report.

The woman read her victim impact statement to the court.

She said the abuse affected every aspect of her life.

"I don't think there will ever be a time in my life when I'm not affected by this crime," she said.

The woman said she often felt disconnected and isolated from others.

"I didn't know what was happening to me was wrong at the time, but I know I felt scared and uncomfortable," she said.

"I believed it was my shameful secret and it's a burden I've had to carry on my own."

The woman said as a result of the abuse, she developed an eating disorder, and suffered from depression and anxiety.

She also has nightmares and flashbacks of the abuse.

"My eating disorder was born out of a scared little girl trying to manage painful memories and emotions," she said.

"My childhood was taken away from me."

Prosecutor Joanne Piggott argued the abuse happened in a place where a child should have felt safe.

"This was in a place where a child should be safe, nurtured and completely free from harm," she said.

"It should have been a place of happiness and fond memories."

The court heard that once the victim's mother was aware of the abuse, she confronted the man, who apologised for his actions.

The man also wrote letters of apology to the victim and her mother.

Judge Michael Cahill said the offending had brought great shame to an otherwise law-abiding family.

He said the matters were extremely serious.

"A term of imprisonment is the only appropriate sentence, but it is open to me to consider if that is served immediately or suspended," he said.

The man will be sentenced on Wednesday.

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