The young Magpies were due to face their Black Cats counterparts at the Eppleton Colliery Welfare Ground on Monday, 7th January 2019.
But Newcastle's second-string have been drawn against Sunderland's first team in the Checkatrade Trophy - kick-off at the Stadium of Light is 7.45pm (GMT) on Tuesday, 8th January - so the Premier League 2 fixture has now been brought forward.
It will now be played at 1pm (GMT) on Friday, 4th January. The venue will be Sunderland's Academy of Light training ground, with no public admission.
The Magpies were 5-0 winners when the two sides met at St. James' Park in August.
For clarification, the Checkatrade Trophy tie between Sunderland's first team and Newcastle's under-21 side remains at the Stadium of Light on Tuesday, 8th January with a 7.45pm (GMT) kick-off.
Newcastle's full second-string fixture list can be viewed here.