Ishe Samuels-Smith featured for Swansea City during the previous campaign while on loan.
The 20-year-old defender Samuels-Smith has arrived at Meadow Lane from Chelsea, capable of filling various positions down the left flank. Hindolo Mustapha, also 20, has come in from Crystal Palace, having ended his temporary stint at Wigan Athletic early.
Mustapha operates as an attacking midfielder and has represented Sierra Leone internationally. Samuels-Smith has previously featured for England at Under-20 level.
Both players have joined the Magpies as the club prepares for its return to League One for the first time since the 2014-15 season.
The Crystal Palace prospect Mustapha also spent time on loan at West Bromwich Albion last term.
Richard Montague, the club’s director of football, said on the club’s official site that Samuels-Smith is a promising young talent able to make an impact in both offensive and defensive situations.
Montague noted that Mustapha had been among the club’s primary objectives during the current transfer window.