Wall provided the true dagger with 4.9 seconds left when he hit a 20-foot, pull-up jumper, providing the final points.
When Dorell Wright missed a three-point shot at the buzzer, the Wizards had secured another win with Wall on the floor.
Wall's presence has meant everything for Washington. He missed the first 33 games with a knee injury and the Wizards went 5-28 in those games.
Since his return, the Wizards are 14-11.
"We had some bad breaks, and John, like he always does, makes things happen, got to the foul line and made big shots," Sixers point guard Jrue Holiday said.
Wall ended with 16 points, six assists and two turnovers. He shot 7 for 11 from the field.
The book on Wall is to back off him and make him beat you with the jump shot.
"I have been more comfortable taking shots [late in the game] and have to keep having confidence knocking them down," Wall said. "I know teams play off me and I have to have confidence shooting."
Speaking of the confidence, the Sixers could have gained quite a bit with a win. They haven't won consecutive games since Feb. 4 when they captured their third in a row with a 78-61 victory over visiting Orlando.
Now 23-35, the Sixers were admittedly fatigued by playing their sixth game in nine days.
Holiday shot just 4 for 19 from the field and said the team was affected by fatigue.
"I think we weren't as active and alert - and personally, I wasn't," Holiday said.
To their credit, the Sixers, who trailed by eight points with less than eight minutes left, kept fighting.
With 24 games left, that at least is a good sign in a season that hasn't had many.
After their effort was questioned in the much-publicized postgame news conference by coach Doug Collins after a 98-84 home loss to Orlando last Tuesday, the Sixers have played hard if not always well the last three games. They lost in Chicago, 93-82, overcame a 16-point deficit to beat Golden State on Saturday, and played a competitive game with the Wizards.
The bench played well, outscoring the Wizards reserves by 30-17, with Wright scoring 15.
In the end, the Sixers couldn't contain Wall, who showed the impact one difference maker can have on a franchise.
Contact Marc Narducci at firstname.lastname@example.org. Follow @sjnard on Twitter.