Jayden Stockley scored either side of halftime as Charlton came out of Tyneside with a victory over the seventh-division minnows to advance to the third round for the second time in three years.
Story of the match
Charlton caretaker manager Johnnie Jackson made four changes from the side that faced Shrewsbury Town in their last league outing with Stephen Henderson, Deji Elerewe, Diallang Jaiyesimi and Stockley all coming into the starting lineup.
The visitors had the first sight of goal in the 14th minute as Conor Washington set Stockley up for a chance, but his shot lacked conviction and was easily handled by Jacob Chapman.
Gateshead then had their first opportunity through some neat build-up play, the ball eventually being worked to Cedwyn Scott, but he could only find the side netting with his shot.
More fine link-up play saw Macaulay Langstaff centering for Adam Campbell at the far post, but his curling effort went over the crossbar.
The Addicks then broke the deadlock when Akin Famewo found Washington and after he got behind the Heed defense, drove to the byline and his cross was headed home by Stockley.
Henderson was then called into action just before halftime as he denied Campbell, who then skewed the rebound wide.
Just after the break, the non-league outfit again threatened as a low drive by Alex Nicholson was saved by Henderson, who skewed it to Langstaff, but his first-time shot was wide.
At the other end, Alex Gilbey cut back for Washington, who was in a good position, but his chance was straight at Chapman, who had no trouble gathering it in.
Moments later, the Addicks doubled their lead, Jaiyesimi's center finding Ben Purrington and his volley just nicked Stockley on the way through.
Luke Williams then sent in a lovely through ball that Langstaff got on the end of, but with the goal at his mercy, he could only fire over.
Henderson made a brilliant double save as time ticked away. First, he stopped substitute Jack Hunter and after Mike Williamson rattled the left upright, he stoned Louis Storey.
Man of the match: Jayden Stockley
He showed great skill in getting on the end of Washington's cross to head home and was a bit fortunate to grab a second, but he made the most of Jackson naming him in the starting lineup.