Ronnie McCormack scored the winning try six minutes into injury time as Ireland A snatched third place in the Churchill Cup tournament in Edmonton.
Jamie Heaslip tries to break through the England line
They capitalised when two Saxons players were sin-binned for collapsing mauls as prop McCormack was driven over by the rest of the pack.
England led 22-13 at one stage and thought they had sealed it when centre Ben Johnston went over late on.
But Ireland's staying power proved decisive in a physical encounter.
Both sides lost players because of injuries, with Ireland's Ray Hogan suffering a suspected broken right leg and England coach Jon Callard forced to empty his bench of replacements.
They also scored four tries each with Kai Horstmann, Ayoola Erinle and Sam Vesty crossing for England before Johnston's last-minute touchdown, and Jamie Heaslip, Matt Cullough, John Fogarty and McCormack going over for the Irish.
Saxons coach Callard was understandably frustrated by a second defeat in three matches, even if the likes of Horstmann and flanker David Seymour pressed their claims for senior recognition during the tour.
"It's disappointing - we have got a lot out of the squad and we have a few people who have put their names forward for the bigger picture but this was one of those games where we failed to react to what was going on around us," Callard said.
"It's disappointing to accept because the players have given a lot in such a short space of time and they have come off second best again.
"Defeat is one thing and that pain will go after a couple of days but mistakes have to be rectified and if we learn from those mistakes then it will have been a successful tour."
Ireland A: Cunningham, Maxwell, Hearty, Lawlor, McPhillips, Wallace, O'Leary, R. Hogan, Fogarty, Court, T. Hogan, McCullough, Jennings, McMillan, Heaslip.
Replacements: Blaney, McCormack, Browne, Muldoon, Keane, Hickey, Keogh.
England Saxons: Armitage, Haughton, Johnston, Vesty, Erinle, Walder, Stuart-Smith, Barnes, Buckland, Turner, Hudson, Kennedy, Roche, Seymour, Horstmann.
Replacements: Paice, Ward, Beattie, Narraway, Wigglesworth, Horak, Woods.
Sin Bin: Barnes (75), Paice (80), Beattie (80).