In pursuit of only their third away victory across all competitions this season, Milwall went close to taking the lead shortly after the quarter-hour mark, as George Saville saw his spontaneous strike sublimely stopped by Anthony Patterson.
On the back of their 1-0 victory over Al-Shabab in Dubai, Sunderland struggled to influence their home advantage into the contest, as only Danny Batth’s defensive instinctiveness prevented Tom Bradshaw’s header from opening the scoring.
Amad Diallo should then have tested visiting goalkeeper George Long for the first time in the match, but the on-loan Manchester United winger failed to find his feet at the opportune moment.
With a monumental 17 points from their last eight matches before today’s affair in the North East, Millwall flew out of the tunnel for the second half as Andreas Voglsammer menacingly attempted to mark his name on the scoresheet.
However, Sunderland were ahead in the 53rd minute as Diallo made no mistake this time, clinically slotting Ellis Simms’ enticing cross into an unguarded net.
Not to be deterred by going behind against the run of play, Millwall were inches away from an immediate response as Dan Neil cleared Charlie Cresswell’s header off the line.
After only five victories since Tony Mowbray's appointment at the end of August, Sunderland doubled their lead five minutes later as Alex Pritchard brilliantly directed his strike into the right-hand corner.
Sunderland then put the final sprig of holly on their early Christmas cake in added-on time, when Simms clinically slotted home in his one-on-one battle with Long beyond the grasp of the Millwall goalkeeper.
The victory moved Sunderland into the top half of the Championship standings.
In contrast, Millwall suffered the unfamiliar taste of defeat after succumbing to only their second defeat in 10 league matches.
