Newell's remain three points clear of River Plate, who lost 2-0 at Argentinos Juniors on Sunday, and Lanus, held 0-0 at home by Belgrano.
With three matches to go, Newell's lead the standings with 32 points, River and Lanus have 29 apiece with San Lorenzo and Godoy Cruz two points further back.
All Boys went ahead when Newell's goalkeeper Nahuel Guzman flapped at a left cross, missed it and All Boys defender Jonathan Ferrari scored with a spectacular overhead kick in the 35th minute.
Four minutes later, All Boys goalkeeper Nicolas Cambiasso tipped over a shot from Maxi Rodriguez in the best chance of the first half for Newell's, who have gone three away matches without a win.
All Boys went two up on the hour when defender Maximiliano Coronel met a free kick from the left with a looping header that sailed over Guzman into the top far corner.
Newell's pulled one back in the 78th minute when Cambiasso could only parry a stinging shot from Rodriguez and left back Milton Casco netted the rebound.