Millwall were 2-1 victors at Bristol City in the Sky Bet Championship on Tuesday night at Ashton Gate.
Jed Wallace scored in the 11th minute to give The Lions the lead in BS3, with Jake Cooper heading home his first of the season 20 minutes from time to put Gary Rowett's side two to the good.
Robins substitute Callum O'Dowda reduced the arrears with 84 minutes played, but Millwall defended heroically in the closing stages to claim another away win.
Gary Rowett made three changes from Friday night's draw with Nottingham Forest, as Shaun Hutchinson, Tom Bradshaw and Jon Dadi Bodvarsson came in for Ben Thompson, Jiri Skalak and Matt Smith - the trio taking their places on the bench.
Three minutes in, slack defending from The Lions nearly allowed the hosts a clear run at goal, but the quick thinking of Bartosz Bialkowski to narrow the angle allowed Millwall's defence to rush back and clear.
At the other end Mahlon Romeo crossed for Bodvarsson, but the striker's looping header landed on the roof of Daniel Bentley's net, before Jayson Molumby's volley - heading wide - was touched out of play by Ashley Williams, with the resulting corner-kick coming to nothing.
With 11 minutes on the clock, Millwall took the lead. Shaun Williams' tackle in the middle of the park won the ball back and sent Romeo down the right-hand side - his through-ball found Jed Wallace, who slotted past the dive of Bentley for his eighth goal of the campaign.
The Lions were the better team as the midway point of the half approached, and a superb passing move which began with Murray Wallace and took in Williams, Hutchinson and Jed Wallace nearly ended with Bradshaw forcing the ball home, but the cross just evaded him.
The hosts were enjoying a brief spell of pressure as the half-hour mark came and went, but the best they could muster was Josh Brownhill's effort from distance, which comfortably sailed past Bialkowski's left-hand post.
Millwall were attacking with pace, direction and power, though, and a mistake from Adam Nagy nearly allowed The Lions in for a second, but the City defence scrambled the ball away. Close control from Bodvarsson then set up a cross to the back post, but it was too high for the head of Bradshaw.
Hutchinson then headed over from a Williams corner as the final minutes of the first-half came into view, with Famara Diedhiou bringing Bialkowski into action for the first time a minute later, heading at the Pole.
More indecision in The Robins' defence then allowed Romeo a run at goal with 40 minutes on the clock, but his first touch took the ball too wide of goal, with his eventual shot sailing wide.
Nagy had the first effort of the second-half for Bristol City, but the ball rolled wide without troubling Bialkowski. The Lions were enjoying large spells of possession after the restart, however, and a momentary scramble in the penalty area following a Williams corner saw a number of players attempt to nod the ball home, but to no avail.
There were 57 minutes played when a cross into the box looked destined to meet the head of Brownhill to equalise, but a combination of captain Alex Pearce and Jake Cooper kept the ball from nestling into the back of the net. Diedhiou then struck wide as the home side looked for a way back into the match.
In a game that was beginning to become stretched, Romeo looked to provide the assist for Bradshaw, but the striker was unable to make a clean connection from the cross from just outside the six-yard box.
With 20 minutes remaining, though, The Lions had their second - finally, through the head of Cooper for the first time this campaign. After Romeo won a free-kick on Millwall's right, Jed Wallace swung the ball to the back post, where the towering defender was there to head home.
Bodvarsson and Jed Wallace then both had half-chances to extend the lead, before the latter was sent on goal by substitute Matt Smith with 13 minutes remaining, but his shot was saved by Bentley.
With six minutes remaining City were level, as O'Dowda - despite Bialkowski getting to his effort - found the net via the post. From there, the pressure cranked up many notches, with The Lions' stopper having to palm away a Brownhill effort from distance, before the Pole again pulled off a huge save, this time from substitute Pedro Pereira.
After five minutes of stoppage-time, referee Gavin Ward called time on the game and a heroic period of defensive work - The Lions have their second away victory of the season and seven points from nine on the road.
Bristol City: Bentley, Hunt (Pereira 86'), Nagy, Baker, Brownhill, Diedhiou, Weimann, Eliasson, Rowe (O'Dowda 76'), A. Williams, Massengo (Palmer 65'). Subs not used: Maenpaa, Watkins, Semenyo, Moore.
Scorer: O'Dowda 84'
Millwall: Bialkowski, M. Wallace, Hutchinson, Cooper, S. Williams, J. Wallace (Mahoney 89'), Bradshaw (Thompson 77'), Romeo, Pearce, Molumby, Bodvarsson (Smith 76'). Subs not used: Steele, Brown, O'Brien, Skalak.
Scorer: J. Wallace 11', Cooper 70'
Booking: M. Wallace
Referee: Gavin Ward
Attendance: 19,742 (352)