Video: YouTube user nhlsarok
Henderson left his boyhood club in 2011, whilst Mignolet swapped Wearside for Merseyside in 2013.
A ninth minute Lazar Markovic goal separated the two sides in windy conditions in the North East.
“It was a good win, we knew it would be difficult for us,” Henderson told BT Sport 1 after the game. “In the first half we controlled the game and we dug in near the end. Markovic has great potential, he works hard, you see the quality he has going forward.”
Mignonette meanwhile was delighted to have kept a clean sheet: “It was windy today so you have to get through it and to keeping a clean sheet in the manner we did and difficult conditions was a great team effort.”