Isaac Olaofe and George Alexander (2) were on target as Millwall's Under 23s defeated Cardiff City 3-0 in the Professional Development League on Monday afternoon at Calmont Road.
Despite a lacklustre Lions performance, Kevin Nugent's side gained another three points to keep themselves in the second and final promotion spot in the Southern Section of the League.
Olaofe nodded home a Jiri Skalak corner-kick to give Millwall a first-half lead, before Alexander netted his double - first from the penalty spot before taking advantage of a fortunate deflection - after the break to secure the win.
Nugent was able to call upon Skalak and Billy Mitchell for the visit of The Bluebirds, with the first chance of the game for The Lions falling to Harry Ransom, but he headed over the crossbar.
Sion Spence and Mark Harris looked the most likely for Cardiff but both were unable to score - the latter forcing Ryan Sandford into a smart save - with the stopper at his best again as he saved from Shamar Moore after the winger beat two Millwall men and shot towards goal.
With 37 minutes on the clock Millwall were in front, as Olaofe rose highest to head Skalak's corner past Warren Burwood.
Kieron Evans had the opening opportunity of the second-half but Sandford was again strong, before The Lions were given a chance to double their lead on 73 minutes as Alexander was bundled over inside the penalty area. The striker picked himself up, dusted himself down and rifled home Millwall's second, despite Burwood guessing correctly.
Five minutes from time it was three - and in slightly fortunate circumstances - as Burwood's parry from Mitchell's shot hit Alexander and went in.
Next up for Millwall's Under 23s - who currently sit four points in front of Charlton Athletic and Coventry City, although The Sky Blues have two games in hand - is a local derby with Crystal Palace at Calmont Road on Tuesday 18th February.
Millwall: Sandford, Brown, Tiensia, Mitchell, Ransom, Strachan, Duncan, Skeffington (Burey 58'), Alexander, Olaofe, Skalak. Subs not used: Topalloj, Wright, Moss.
Cardiff City: Burwood, Coxe, Pryce, O'Almeida, Jones, Bodenham, Evans, Wootton (King 71'), Harris, Spence (Williams 66'), Moore (Kavanagh 59'). Sub not used: Stewart.
Referee: Mr. R Whitton