The Addicks moved up to eighth in League One with their first home win in nine at The Valley on Tuesday evening.
A second-half double from Conor Washington wrapped up all three points as the Addicks showed strong defensive unity to overcome the opposition, who grabbed a late consolation deep into injury time.
The first chance of the game came to the Addicks in the opening minutes as Ian Maatsen’s cross from the left found Jayden Stockley in the middle. The striker headed down to the left, but his show was held Jonathan Mitchell in the Cobblers’ goal.
The visitors nearly found the breakthrough 25 minutes in as a good bit of build-up play saw the ball end up at the feet of Peter Kioso out wide. The defender took a touch into the box and unleashed a powerful outside of the foot shot, which skimmed past the left-hand post.
Charlton came out the brighter of the two sides in the second half with Liam Millar being fouled outside of the Northampton box. The resulting free-kick saw Jake Forster-Caskey step up to strike towards goal. However, the midfielder’s left-footed shot just curled wide of the goal.
The Addicks were awarded a penalty in the 65th minute following a corner. Albie Morgan whipped in the set piece, which was cleared towards the edge of the box. The onrushing Forster-Caskey was clattered to the floor and the referee pointed to the spot, giving Charlton a golden opportunity to break the deadlock in a fairly uneventful match.
Washington stepped up confidently to pass the ball into the bottom right corner, past the diving Mitchell to make it 1-0 to the Addicks.
Charlton came close to doubling the lead late on through substitute Chuks Aneke. The big man got onto a cross from fellow sub Andrew Shinnie, but his powerful header was palmed over the bar by the Northampton goalkeeper, a fine reflex save.
A minute later, Charlton added a second. Aneke rolled a ball to the edge of the box, finding Shinnie, whose strike was palmed away by Mitchell. Washington was quick to pounce and fired the ball home from seven yards out to bag his second of the game.
The visitors added a consolation in stoppage time from a corner. Substitute Alex Jones leaped higher than anyone else to meet a Mark Marshall corner and loop a header over Ben Amos.
The victory sees Charlton move up to eighth in the league table, one point behind Portsmouth in sixth, who have a game in hand.
Charlton: Amos; Gunter, Pearce, Pratley, Maatsen; Forster-Caskey (Shinnie 76’) Watson, Morgan (Smith 89’); Millar, Stockley (Aneke 66’), Washington (Schwartz 89’).
Subs (not used): Harness, Oshilaja, Jaiyesimi.
Goals: Washington (68’ pen, 85’)
Booked: Morgan 44 (foul), Aneke 90 (unsportsmanlike conduct)
Northampton: Mitchell; Kioso, Jones, Horsfall, Harriman; Sowerby, McWilliams (Rose 73’), Watson; Hoskins (Marshall 73’), Edmondson (Jones 89’), Miller.
Subs (not used): Arnold, Morris, Korboa, Bolger.
Goal: A Jones
Booked: Kioso 40 (foul), Edmondson 70 (foul)
(Report by Nick Emms)