Ryan Fredericks made a dream debut scoring the only goal of the game to mark new manager Ian Holloway's first game at The Den with a win.
Right-back Fredericks signed on loan from Tottenham Hotspur on Friday morning and went straight into the Millwall team - one of four changes made by Holloway following last Saturday's defeat by Huddersfield Town.
And it proved to be a master-stroke as Fredericks marked his first start for The Lions with the all-important winner on 39 minutes, a speculative cross-shot that floated over the head of Ipswich keeper Dean Gerken and into the far corner.
Victory was no more than Millwall deserved as they produced a high-tempo display brimming with effort, enthusiasm and passion.
The Den faithful played their part too, creating a fantastic atmosphere long before the opening whistle and gave Holloway a rousing reception as he took his place in the home dug-out.
From the first minute to the last The Lions responded to their new manager perfectly, showing real purpose going forward and defending in numbers.
Ipswich suffered an early blow when Jay Tabb was stretchered off after 11 minutes and as they struggled to re-group, Liam Trotter went close to breaking the deadlock with a curling shot that flew narrowly wide.
The visitors created a couple of half-chances with David McGoldrick and Daryl Murphy both denied by keeper David Forde, who comfortably held both efforts.
However it was Forde's opposite number Gerken who did end up picking the ball out the back of the net six minutes before the break. Fredericks picked up possession on the right, sprinted forward and despatched a deep cross that to pretty much everyone in the ground, looked to be floating wide. It didn't, however, and the ball dropped over the head of Gerken and into the back of the net.
Moments after the goal, The Lions were dealt a blow when Forde hobbled off with a thigh strain to be replaced by Stephen Bywater for his first appearance since August.
Millwall continued to press forward after the break but it was Ipswich who came close when Tommy Smith’s header was cleared off the line by former Lee Martin.
Former Tractor Boy Martin nearly doubled Millwall's tally moments later when, following great work from Andy Keogh and Scott McDonald, he turned on a sixpence but inexplicably lashed the ball over the bar from barely six yards.
The visitors nearly grabbed a leveller that they really did not deserve as the game headed towards the final whistle, but Bywater was equal to to Paul Taylor's angled drive, brilliantly blocking at his near post and in doing so, securing a vital victory for The Lions and welcome clean sheet.
Millwall: Forde (Bywater, 44mins), Fredericks, Malone, Shittu, Lowry, Martin, Bailey (Wright, 61mins), Trotter (Abdou, 69mins), Keogh, Morison, McDonald. Subs not used: Feeney, Woolford, Beevers, Marquis.
Fredericks (39mins) Scorer:
Ipswich Town: Gerken, Cresswell, Chambers, Smith, Berra, Edwards (Taylor, 62mins), Skuse, Murphy, McGoldrick, Tunnicliffe, Hyam (Tabb, 12mins (Nouble, 73mins)). Subs not used: Loach, Anderson, Hunt, Mings.
Bookings: Edwards (45+6mins), Taylor (88mins)
Att: 12,125 (away 1,298)