Both teams struggled for fluency throughout the low-scoring clash, but the Lions broke the match open with a six-goal final quarter.
Melbourne had led by a game-high 14 points early in the final term, but had no answers to the Lions' fourth quarter onslaught.
However, the Lions dominated the inside 50 count 60-34 and it eventually told in the 11.8 (74) to 6.15 (51) triumph.
"I didn't think it (inside 50s) would get us over the line. I was just hoping that we were able to find a way through," Lepptisch said post-match.
"We were just efficient (in the last quarter). That's pretty much the game in summary. We had a lot of inside 50s – we smashed them in that area – and they smashed us in efficiency inside 50.
"The encouraging signs are things we're working on now are smaller things as opposed to the big-ticket stuff.
The Lions had only kicked five goals to the final change but they broke the shackles in the last quarter and more than doubled their score.Rohan Bail put the Demons 13 points up two minutes into the last quarter and the Dees looked to have done enough.
But Daniel Merrett, who was reported for a late hit in the fourth term that left Cam Pedersen with a suspected broken nose, had other ideas.
The Lions spearhead kicked truly at the nine-minute mark, sparking a six-goal run with Jed Adcock, Michael Close, Daniel McStay, Ryan Harwood and Lewis Taylor getting in on the act.
Tom Rockliff was outstanding for the Lions with 32 disposals, while Rohan Bewick put in a solid four-quarter effort on the wing and finished with 27 touches.
Pearce Hanley again showed his class across half-back with 24 touches and Daniel McStay booted three goals.
The Lions notched their third win from the past five games, while the Demons have now not won at Etihad Stadium since round 19, 2007.
MELBOURNE 3.3 4.8 5.13 6.15 (51)
BRISBANE LIONS 3.3 4.3 5.6 11.8 (74)
GOALS
Melbourne: Kent 2, Frawley, N. Jones, Tyson, Bail
Brisbane Lions: McStay 2, Close 2, Beams, Hanley, McStay, Merrett, Adcock, Harwood, Taylor
BEST
Melbourne: Howe, N. Jones, Tyson, Frawley, Terlich,
Brisbane Lions: Rockliff, Bewick, Martin, Adcock, Hanley, Gardiner, McStay
INJURIES
Melbourne: McDonald (ankle), Pedersen (nose)
Brisbane Lions: Maguire (foot)
SUBSTITUTES
Melbourne: Jay Kennedy-Harris replaced Luke Tapscott in the third quarter
Brisbane Lions: Ash McGrath replaced Ryan Lester in the third quarter
Reports: Daniel Merrett (Brisbane Lions) reported for striking Cam Pedersen (Melbourne) in the fourth quarter
Umpires: Donlon, Harris, O'Gorman
Official crowd: 18,079 at Etihad Stadium
