Christian Norgaard initially treated a boisterous home crowd to a fine goal by curling precisely into the top corner midway through the first half, but two Liverpool substitutes combined to produce an equaliser by Kristoffer Peterson mere moments after the restart.
But Ferhan Hasani had the final say in stoppage time, jinking beyond a succession of challenges and blasting into the roof of the net with two minutes to play to consign the visitors to a loss on their first outing of the campaign.
Brendan Rodgers had selected a 23-man squad for the journey to Scandinavia and the eye-catching names in his chosen XI at the Brondby Stadion were Tiago Ilori and Jordan Rossiter - both handed chances to impress in a side mixing youth and experience.
Trademark dribbling technique from Philippe Coutinho in the opening minutes almost brought rewards when the Brazilian slipped an incisive pass into the grateful Fabio Borini. The No.29 was crowded out at the crucial moment, however, and the chance passed for the Reds.
Equally tricky was Norgaard at the other end, sliding past Lucas Leiva and winning a free-kick that was ultimately dealt with by Brad Jones when Riza Durmisi curled to the near post. The lively Coutinho was off target when he drilled towards goal in response.
On the quarter-hour, Suso took proceedings by the scruff of the neck. Taking possession on the right flank, the young playmaker skipped inside and drove forward, before utilising the freedom to crack a left-footer that had to be pushed around the post with fingertips by Brondby goalkeeper Lukas Hradecky.
Rodgers was forced into an early change on 21 minutes when Ilori limped off with an injury, and it was recent Academy recruit Kevin Stewart who was selected to enter the action, with Martin Kelly moving into the centre to partner Daniel Agger in defence.
Further disappointment followed moments later. A looped ball into Liverpool territory bounced loose on the edge of area and Suso's attempted clearance carried to Norgaard, who instantly dispatched a swerving effort from distance that sailed beyond the stretch of Jones.
The Reds were unsure how they hadn't equalised shortly after; Borini's side-foot shot was blocked by Martin Albrechtsen, Hradecky thwarted a blistering hit by the supporting Brad Smith from the left and rose quickly to punch out Coutinho's follow up and preserve the home team's advantage.
As the break approached, Smith surged forward once more - zipping into the penalty box to collect a pass and fire, but found a Brondby opponent blocking his path. Fredrik Semb then put his body in the way to stem a low cross from the Australian-born full-back.
Hradecky was the visitors' nemesis yet again in the closing seconds of the period, beating out a daisy-cutter from Lucas after the midfielder had punted from 20 yards, with Borini denied by the 'keeper too on the rebound. So, 1-0 at half-time it was.
The manager overhauled his XI with 10 changes at the break and his decision paid dividends immediately. Jordon Ibe sped all the way along the left channel and into the danger zone, then perfectly teed up Peterson to calmly find the back of the net from close range on 48 minutes.
Backed by the additional fitness of being further into their pre-season, Brondby were proving obdurate opponents and Thomas Kahlenberg could consider himself unfortunate when a whipped free-kick from range drifted narrowly wide of the right post as Jones launched to his left.
Ibe threatened to convert without assistance as the game approached its final quarter, gliding inside and outside a series of tackles but sending his strike too close to Hradecky. Back came the Danish outfit and Durmisi caused problems from another set-piece, directing the ball off the crossbar with a beautiful curler.
A lung-busting run down the left by Jon Flanagan concluded with the collection of Ibe's set-up and the Scouser sought to find Peterson for a similar play to the one that secured a leveller, but it wasn't to be for the forward on this occasion.
Neither team were settling for a draw. First, the Brondby stopper kept out Ibe when the 18-year-old looked a certain scorer, then Ferhan Hasani took free-kick duties for the hosts and, like Durmisi before him, struck the woodwork with a sublime shot.
But the No.22 was not to be denied and an unstoppable, lengthy dribble by Hasani carried him into the heart of the Liverpool area, where he made no mistake by blasting high into the roof of the net to claim the victory.