A fan favourite as a player, Brebner took over as interim coach ahead of the A-League season restart and led a decimated Victory side to one win and four losses in the NSW hub.
"We are excited to have someone who bleeds blue at the helm, and strongly believe Grant is the right person to lead our A-League program," Victory chairman Anthony Di Pietro said in a statement.
"There's plenty of hard work ahead as we prepare for our AFC Champions League campaign and the upcoming 2020-21 A-League season, but it is exciting to finalise Grant's appointment, so we can now look to collectively build our squad and the required support staff, to position our club for success.
"Grant is clear in the style of football Melbourne Victory want to play, and most importantly he has already started building the foundations and culture he believes will help us return to delivering the on-field results expected at our club."
Brebner, 42, enjoyed a stellar career as a Victory player between 2006-2012, winning the A-League premiership-championship double in 2006-07 and 2008-09.
He was involved in the club's academy coaching set-up for six years, then worked as an assistant to previous interim coach Carlos Salvachua.
Brebner took over as interim in June after Salvachua returned to Europe and initially didn't put his hat in the ring for the permanent position.
But following the season restart, he expressed his interest in the full-time role.
"The club has been a huge part of my life, and the experience of coaching the team over the past couple of months really fuelled my desire and belief that not only did I want the opportunity to secure the role full time, but that I had the skills and expertise to do so, and to do it well," Brebner said.
"I have made no secret of the fact that I feel like the club had strayed from its football identity and culture, and I want to help lead the solution."
Brebner faces the massive task of rebuilding Victory, who finished 10th this season.
He could lead Victory relatively quickly, with the club scheduled to continue their postponed Asian Champions League campaign in a hub in Malaysia in October.