Robert "Locky" Eccles, 72, was found guilty by a jury in April of four child abuse charges and handed a prison term of up to four years and eight months on Monday.
He mouthed "I'm alright" to four female supporters in court as he was handed his fate.
The Gunditjmara elder received a Senior Victorian of the Year award in 2021 for his "intergenerational leadership, sharing language, culture and his passion for sport with the community".
However, Minister for Ageing Ingrid Stitt had since revoked the award and requested he return his trophy and certificate, the court was told.
Eccles founded the Gunditjmara Aboriginal Co-operative and was appointed as an elder to Koori court hearings in the county and magistrates courts in 2016.
He continued in the role until 2023, when he was charged.
Eccles was also called upon by private and government organisations to deliver programs and Welcome to Country ceremonies as an elder, the court was told.
"Yours has been a spectacular fall from grace," Chief Judge Amanda Chambers said on Monday.
Eccles was aged 59 and working as a senior umpire in regional Victoria when he started giving full body massages to a 15-year-old junior umpire in his garage in 2011.
He had mentored the teen through the local umpires association and told him the massages were important for his performance as an umpire.
When the youth turned 16, the massages became sexual.
Eccles sexually offended against the teenager on two occasions in 2012 and warned him not to tell anyone.
The victim did not report the abuse until January 2023, when he informed his partner and police after Eccles texted him saying: "Hey mate, how are you going?"
Eccles' first trial, in October 2024, was abandoned after the judge discharged the jury as she found evidence adduced by the informant to be prejudicial.
His second trial resulted in a unanimous guilty verdict for four charges.
He was convicted of three counts of committing an indecent act on a child aged under 16 and one of sexual penetration of a 16 or 17-year-old child under his care.
The jury acquitted Eccles of another four charges of sexual penetration of a 16 or 17-year-old and one of committing an indecent act.
Judge Chambers took into account Eccles' previous good character, which was demonstrated through a number of references handed to the court.
He was a respected community member who had provided a significant contribution to Indigenous recognition and advancement, she added.
However, offending against a child he had mentored and encouraged was "appalling", particularly given the inherent power imbalance, Judge Chambers said.
The fact the offending happened in the privacy of Eccles' home, where the boy could not be protected, had amplified his vulnerability, she said.
"Your offending involved the breathtaking breach of the trust that the association ... the victim's parents and grandmother had placed in you," Judge Chambers said.
"What you did was so egregious that it is nonsensical to suggest you may not have fully appreciated the wrongfulness of your conduct."
She found Eccles' offending had left a "profound impact" on the life of his then-teenage victim.
"I often sit and reflect on what life could have been, but there is one thing for sure, I will never be the same again," the victim, who cannot be named, said in a statement.
Eccles, who continues to maintain his innocence, must spent a minimum of two years and 11 months in jail before he will be eligible for parole.
He has already served 67 days of this sentence and he will be registered as a serious sex offender for life.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
Kids Helpline 1800 55 1800 (for people aged 5 to 25)
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