Town moved back into the automatic promotion places with a deserved win at the New Den.
Noel Hunt gave Blues the perfect start with the opener on six minutes after good work by his brother Stephen and two were involved again on the quarter hour, with Noel grabbing his second.
Magaye Gueye got Millwall back in the game on the stroke of half-time but Jonathan Parr’s excellent finish 13 minutes from time sent Town back into second place in the Championship.
David McGoldrick and Luke Hyam were both missing from the team that went out of the FA Cup to Southampton in midweek through injury.
Cole Skuse was named in the squad of 18 and travelled but a recurrence of the illness that kept him out of action last week saw him sidelined, with Blues naming just six substitutes.
Noel Hunt was handed his first start, with Jay Tabb and Paul Anderson returning to the team as Blues kicked off with a 2500 following at the New Den.
Diego Fabbrini, making his debut for the Lions on loan from Watford, had a shot deflected into the air that was half cleared by Bart Bialkowski, the Italian striker sending a left foot follow up just wide from 15 yards.
It was Town that struck first though, Noel Hunt sliding his shot past David Forde after brother Stephen had forced the ball over the Lions’ defence.
Town extended the lead 10 minutes later, Noel Hunt threw himself at his brother’s cross but couldn’t get his head on it, but he reacted quickest when Kevin Bru fired across goal to tap the ball in from three yards.
Stefan Maierhofer headed well wide from a free-kick as Millwall looked to get a foothold in the game but it was Town who continued to look a threat, Paul
Anderson seeing an overhead kick deflected wide after Noel Hunt had been denied a hat-trick chance.
Anderson had a header saved by Forde as Blues looked to seal the points before the half hour, Stephen Hunt then almost getting on the end of Byron Webster’s back pass.
Maierhofer’s run down the right set up Gueye who fed the supporting Jimmy Abdou in the Lions’ best chance of the first 40 minutes but the midfielder blazed his shot wide. Anderson doing the same at the other end from an equally good position.
Daryl Murphy latched on to in-decision in the home defence but his shot slipped past the far post as Blues continued to carve out openings but just before the break the Lions got a lifeline, Gueye getting on the end of Maierhofer’s flick on to find the net via the post.
Town could have added to the advantage inside the first couple of minutes of the second-half getting underway, Anderson’s driving run released Noel Hunt, his cross wasn’t dealt with and both Murphy and Anderson threatened to find the net before Forde ended the danger.
Forde was off his line to clear from Bru 40 yards from goal on Millwall’s left wing, the ‘keeper having a more comfortable time dealing with Murphy’s shot.
Tommy Smith defended well to clear from Jack Powell’s wicked cross, Tyrone Mings staying equally strong to get in the way of Gueye’s shot then Webster headed wide from the corner.
Freddie Sears came on for his debut on the hour, Parr joining him with both Hunts making way. Former Blue, Lee Martin, replacing Fabbrini for Millwall in a flurry of changes.
Sears saw his shot blocked by Dan Harding’s covering challenge as he latched on to Murphy’s ball over the top, Lee Gregory then showing a good touch to get on the end of Forde’s excellent delivery but Abdou’s shot went wide.
Town made it three on 77 minutes and right in front of the Blue Army, Sears finding Parr with a clever touch and the Norway international did the rest with a cool finish.
Matt Clarke came on for his League debut, the excellent Anderson making way. Bru tested Forde at his near post as Blues looked for a fourth before a final blast of the whistle left the Blue Army in good voice. Chants of ‘the Town are going up’ echoing around the New Den.