Barnet deserved their win, with Mark Byrne and Joe Devera also going close.
Marc Richards wasted a chance for Vale with the score goalless but, with their play-off hopes effectively over, they were a poor second at a feisty Barnet.
The result ensured that the Bees avoided relegation on the final day of the season for the second successive year.
However, the difference with 2010 is that Barnet did not have their fate in their hands on Saturday, but had to rely on Aldershot defeating relegation rivals Lincoln.
Word seeped through in the second half that the Imps were losing, helping to create a triumphant atmosphere inside Underhill as the north London side extended their stay in the Football League for at last another year.
It has been a dramatic and difficult season for Barnet, who in rookie boss Guiliano Grazioli are on their fourth manager of the campaign, but at least it ended on a high note, with the Bees finishing one point above the Imps.
There was an unmistakable passion among the home side, with no-one exemplifying this more than midfielder Sam Deering, who made countless lung-busting runs and last-ditch challenges.
Barnet made the running from the opening whistle but Daniel Leach headed over from a good position, while Clovis Kamdjo twice failed to connect with free-kicks into the area.
The first clear opening of the match came after 24 minutes when Byrne showed great determination to dispossess Ritchie Sutton before bearing down on goal.
Byrne then placed his shot beyond Chris Martin but it rolled agonisingly wide of the far post.
The Bees, attacking uphill in the opening half, appeared to have most of the momentum but they were lucky to escape when Justin Richards' free-kick skimmed the wall and dropped invitingly for Marc Richards, who headed wide when it seemed easier to score.
The hosts refused to be thrown out of their stride and created another good chance when skipper Devera met a free-kick from the left but he headed over the crossbar.
Mark Marshall was a menace down the left and forced a stop at the near post after cutting inside and shooting but it was goalless at the break.
That all changed immediately after the restart when striker McLeod dusted himself down after Gareth Owen had fouled him to put the Bees ahead from the spot.
Barnet pushed hard for a decisive second, with Kamdjo inches away from hooking the ball beyond Vale substitute goalkeeper Stuart Tomlinson, while Rob Taylor made a great block to deny Mark Hughes.
Shortly afterwards a ripple of cheers around the ground indicated that Aldershot had taken the lead against Lincoln, strengthening Barnet's grip on their place in the Football League.
Vale substitute Gareth Roberts cleared off the line and Tomlinson made a superb save from the luckless Byrne before home keeper Sam Walker brilliantly saved at the feet of Marc Richards after Lewis Haldane had played him through.
By that stage the reaction in the stands made it clear that Lincoln had conceded twice more and Barnet saw out six minutes of injury time to claim a deserved victory.
Barnet manager Giuliano Grazioli told BBC London 94.9:
"As a player here, winning promotion was great, winning golden boots, and playing at Old Trafford fantastic occasion but this has surpassed everything.
"the players have been a pleasure to work with credit to them, we had a task in hand to be in it on the last game of the season and to go one better when nobody gave us a chance is fantastic.
"I knew we'd win the game today and it was a great performance under those circumstances, those boys are a great bunch."
Port Vale caretaker manager Mark Grew told BBC Radio Stoke:
"I've just told them that to put in a performance like that is unacceptable to Port Vale Football Club.
"That was an absolute total and utter disgrace of a performance and some of them should count themselves lucky that they have two-year contracts.
"I'm not naming names but some of them haven't given their all for Port Vale Football Club, and I wonder sometimes how they can go home and look themselves in the mirror."
Anthony Griffith challenges Mark Hughes unfairly and gives away a free kick. Jordan Parkes delivers the ball from the free kick right-footed from left wing, clearance by Adam Yates.
Tommy Fraser takes a shot. Save by Stuart Tomlinson.
Outswinging corner taken right-footed by Mark Marshall, clearance made by Anthony Griffith.
90:00 +0:43 Substitution
Substitution Tommy Fraser replaces Mark Byrne.
Effort from the edge of the penalty area by Mark Byrne goes wide of the left-hand post.
Mark Marshall gives away a free kick for an unfair challenge on Adam Yates. Stuart Tomlinson restarts play with the free kick.
Mark Byrne takes the indirect free kick.
Booking Ritchie Sutton is cautioned by the ref for unsporting behaviour.
Ritchie Sutton concedes a free kick for a foul on Mark Marshall.
Free kick awarded for a foul by Gareth Owen on Jack Midson. The free kick is delivered left-footed by Mark Byrne from right wing, Robert Taylor manages to make a clearance.
Substitution Izale McLeod goes off and Charlie Taylor comes on.
Mark Byrne takes a shot.
Marc Richards takes a shot. Save by Sam Walker.
Jack Midson is flagged offside by the assistant referee. Indirect free kick taken by Stuart Tomlinson.
Corner taken left-footed by Mark Marshall to the near post, Daniel Leach has an effort at goal from just outside the box which goes wide of the left-hand post.
Izale McLeod fouled by Lee Collins, the ref awards a free kick. A cross is delivered by Mark Marshall, Izale McLeod produces a header from the edge of the box and misses to the left of the goal.
Substitution Justin Richards goes off and Lewis Haldane comes on.
Corner taken by Mark Byrne.
Mark Marshall takes a outswinging corner to the near post.
Mark Byrne produces a right-footed shot from just outside the box that goes wide right of the target.
Free kick awarded for an unfair challenge on Anthony Griffith by Jack Midson. Gareth Owen takes the indirect free kick.
Mark Marshall takes a shot. Stuart Tomlinson makes a save.
Ritchie Sutton challenges Jack Midson unfairly and gives away a free kick. Jordan Parkes delivers the ball from the free kick right-footed from left channel, Daniel Leach concedes a free kick for a foul on Gareth Owen. Stuart Tomlinson takes the indirect free kick.
Mark Marshall decides to take the corner short.
Mark Marshall takes a shot. Save by Stuart Tomlinson.
Mark Marshall takes a shot. Save by Adam Yates.
Mark Marshall takes a shot. Adam Yates makes a save.
Unfair challenge on Mark Hughes by Marc Richards results in a free kick. Free kick taken by Jordan Parkes.
Substitution Gary Roberts comes on in place of Sam Morsy.
Corner taken by Mark Byrne played to the near post, Ritchie Sutton makes a clearance.
Inswinging corner taken right-footed by Mark Marshall played to the near post, Stuart Tomlinson makes a save.
Free kick crossed right-footed by Sam Deering.
Booking Robert Taylor goes into the book.
Sam Deering fouled by Robert Taylor, the ref awards a free kick.
Jack Midson gives away a free kick for an unfair challenge on Gareth Owen. Gareth Owen takes the free kick.
Substitution Chris Martin goes off and Stuart Tomlinson comes on.
47:18 Goal scored
Goal - Izale McLeod - Barnet 1 - 0 Port Vale Power penalty scored by Izale McLeod. Barnet 1-0 Port Vale.
Gareth Owen concedes a Penalty for a foul on Izale McLeod.
The match restarts for the second half.
45:00 +1:11 Half time
Half Time The referee blows for half time.
Unfair challenge on Joe Devera by Lee Collins results in a free kick. Sam Walker restarts play with the free kick.
Mark Hughes gives away a free kick for an unfair challenge on Sam Morsy. Free kick crossed left-footed by Robert Taylor. Justin Richards is flagged offside by the assistant referee. Sam Walker restarts play with the free kick.
Free kick awarded for an unfair challenge on Sam Morsy by Mark Hughes. Robert Taylor restarts play with the free kick.
Mark Byrne decides to take the corner short.
Justin Richards fouled by Mark Hughes, the ref awards a free kick. Free kick taken by Sam Morsy.
Header from deep inside the penalty area by Joe Devera goes harmlessly over the crossbar.
Free kick awarded for an unfair challenge on Jordan Parkes by Sam Morsy. Mark Byrne takes the indirect free kick.
The referee blows for offside. Sam Walker restarts play with the free kick.
Mark Marshall gives away a free kick for an unfair challenge on Gareth Owen. Chris Martin takes the indirect free kick.
Justin Richards is penalised for a handball. Sam Walker restarts play with the free kick.
Unfair challenge on Louis Dodds by Mark Hughes results in a free kick. Justin Richards produces a strike on goal direct from the free kick.
Unfair challenge on Sam Deering by Robert Taylor results in a free kick. The free kick is delivered left-footed by Mark Marshall from right channel, save made by Chris Martin.
Mark Byrne has an effort at goal from the edge of the area that misses to the right of the target.
Free kick awarded for an unfair challenge on Jack Midson by Robert Taylor. Mark Byrne takes the free kick.
Free kick awarded for an unfair challenge on Daniel Leach by Justin Richards. Free kick taken by Sam Walker.
Free kick awarded for an unfair challenge on Marc Richards by Clovis Kamdjo. Chris Martin takes the indirect free kick.
Foul by Sam Morsy on Mark Hughes, free kick awarded. Jordan Parkes takes the indirect free kick.
Mark Marshall takes a shot. Chris Martin makes a save.
Free kick awarded for an unfair challenge on Mark Marshall by Adam Yates. Mark Byrne delivers the ball from the free kick right-footed from left wing.
Unfair challenge on Daniel Leach by Marc Richards results in a free kick. Indirect free kick taken by Jordan Parkes.
Mark Hughes produces a right-footed shot from just outside the area that goes wide left of the goal.
Marc Richards concedes a free kick for a foul on Daniel Leach. Sam Walker takes the free kick.
Izale McLeod takes a shot. Chris Martin makes a save.
Daniel Leach is caught offside. Chris Martin takes the indirect free kick.
Unfair challenge on Jordan Parkes by Justin Richards results in a free kick. Indirect free kick taken by Sam Walker.
Effort from just outside the area by Mark Byrne goes over the bar.
Ritchie Sutton fouled by Mark Marshall, the ref awards a free kick. Free kick taken by Chris Martin.
Robert Taylor fouled by Clovis Kamdjo, the ref awards a free kick. Louis Dodds takes the free kick.
The assistant referee signals for offside against Jack Midson. Chris Martin takes the indirect free kick.
Sam Deering produces a left-footed shot from just outside the penalty area that goes harmlessly over the target.
Corner taken by Mark Byrne played to the near post, clearance by Gareth Owen.
Shot from just outside the area by Louis Dodds misses to the left of the target.
Short corner taken by Louis Dodds.
The game gets underway.
Live text and data provided by The Press Association
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.