The Addicks were defeated 1-3 by Portsmouth at The Valley this evening.
Charlton goalkeeper Thomas Kaminski was at fault for Portsmouth's opener, allowing Devlin's ambitious dipping strike from 20 yards to squirm through his legs midway through the first half.
Colby Bishop's penalty doubled Pompey's advantage in the 35th minute before Devlin smashed in an excellent swerving effort via the post from 25 yards 11 minutes into the second half.
Stockport loanee Jayden Fevrier pulled one back for Charlton with a fine half-volley but John Mousinho's side held on for victory to move four points clear of the relegation zone with a game in hand, while Charlton remain seven points above Leicester City in 22nd.
Fitting tributes were paid to the late Charlton fan Barker, also known as 'headphones Norm', with a one-minute applause held in his memory before the game.
Harry Clarke had an excellent opportunity to put Charlton ahead after just 38 seconds when he latched onto a long ball forward and hit the target with a first time effort from 16 yards out but was well denied by Portsmouth goalkeeper Nicolas Schmid.
The Addicks had not conceded in their past three games, but Kaminski's error from Devlin's long-range strike gifted Pompey the lead in the 22nd minute to set the visitors on their way to just a third away win of the season from 15 games on the road.
Charlton felt they were hard done by for the penalty award for Portsmouth's second 12 minutes later, claiming left-back Amari'i Bell could not get out the way of a powerful cross by Gustavo Caballero, on his full debut, before former Leamington ace Colby Bishop slotted down the middle from the spot.
After Devlin arrowed in his fifth goal of the season to become Pompey's joint top goalscorer, the Addicks rallied and threatened to create a tense finale when Fevrier pounced on a long throw-in to reduce the deficit with a fine spin and finish 25 minutes from time.
But Portsmouth stood firm for a rare away win and completed the league double over Charlton for the first time since 1985-86.
With only nine goals in 14 away games beforehand and 13 first team players missing through injury, victory could serve as a much-needed confidence boost for Portsmouth in their quest to stay up.
Defeat for Nathan Jones' side ended their three-game unbeaten run and consigned them to only a second loss on home soil in the past seven matches at The Valley.
Nathan Jones told BBC Radio London: "We were poor tonight. We were poor in moments. We had a glorious opportunity after the first minute which would have really set the tone for the night.
"Then we got dominated physically between both boxes. I can moan about the goals because it's gone straight through our goalkeeper, shouldn't go in.
"Second one, it's a penalty that's touched his chest first and then handball. And then they scored another one from distance.
"We have chances from five yards, we probably had better chances on the night but in between both boxes, we got dominated physically and that's not like us."
