Charlton took their tally to ten points from the last four games, following a 2-1 win at Chesterfield on Saturday.
The win lifted the Addicks to 14th place in the table, just a point away from the top half.
The win was more comfortable than the scoreline indicates. Karl Robinson’s side spurned a golden opportunity to go 3-1 ahead when Jake Forster-Caskey missed a stoppage time penalty.
Robinson made two changes from the side that beat Gillingham on Monday, with Joe Aribo and Karlan Ahearne-Grant, coming in for Patrick Bauer and Jordan Botaka, who dropped to the bench.
The changes meant Ezri Konsa dropped back to partner Jason Pearce in central defence.
Charlton took the lead eight minutes before the interval. Aribo fed Forster-Caskey who rifled the ball home from outside the box.
The Addicks doubled their lead after 57 minutes. They were awarded a free-kick on the right, and Ricky Holmes stepped up to place the ball beyond Thorsten Stuckmann.
Charlton were cruising to a comfortable win, but the game had a dramatic finish.
David Faupala robbed Konsa in stoppage time, advanced into the area, but was foiled by Declan Rudd. Unfortunately for the Addicks, the loose ball fell to Reece Mitchell, who tucked it away to halve the arrears.
Charlton launched a counter attack in the last minute of added on time. Botaka broke clear, squared the ball to Forster-Caskey, who was brought down in the area.
The former Brighton man took the spot-kick himself. It was a poor effort that was easily saved by Stuckmann.
Robinson will be looking to end the season on a high, with a win against Swindon next Sunday.
Charlton: Rudd; Byrne, Konsa, Pearce, Dasilva; Crofts, Aribo (Novak 70), Forster-Caskey, Holmes; Ahearne-Grant (Botaka 70), Magennis (Jackson 88).
Subs (not used): Phillips, Barnes, Bauer, Dijksteel.
Goals: Forster-Caskey 37, Holmes 57.
Booked: Aribo 17 (foul), Konsa 84 (scuffle).
Chesterfield:. Stuckmann; McGinn, Hird Anderson, Maguire; Gardner (Brownell 88), Dimaio (Faupala 63), Nolan, Mitchell; Dennis, Rowley.
Subs (not used): Fulton, Ebanks-Blake, Wakefield, Grimshaw, Jones.
Goal: Mitchell 90.
Booked: Dennis 90 (dissent), Nolan (foul).
Referee: Michael Salisbury (Lancashire).
Attn: 5,657 (573 Charlton).
TAGS: Charlton Athletic