Newport will face Wrexham in an all-Welsh Blue Square Bet Premier play-off final after victory over Grimsby.
Christian Jolley scored the only goal of the game on 31 minutes with a low shot which beat James McKeown.
Grimsby started brightly, Tom Naylor forcing keeper Lenny Pidgeley into a save, but Newport were in control once Jolley had broken the deadlock.
Victory sets up a Wembley final against Wrexham to guarantee that a Welsh club will play in League Two next season.
- Victory at Wembley would see Newport regain the Football League status they lost in 1988.
- After being relegated from the old Division Four, they then went bankrupt.
- But the club reformed in its current guise and have risen up through the English league pyramid system.
Holding a 1-0 lead from the first leg, Newport manager Justin Edinburgh kept faith with the side which started at Blundell Park.
The Exiles were also boosted by the inclusion on the bench of top-scorer Aaron O'Connor, who missed the first game through injury.
Grimsby showed three changes, Andy Cook, Cleveland Thomas and the injured Jamie Devitt being replaced by Marcus Marshall, Jay Colbeck and Andi Thanoj.
The Mariners gave two early warnings to Newport, Naylor firing over the bar, while Craig Disley's header was blocked by David Pipe.
Naylor's low shot then forced Pidgeley into a one-hand save to push the ball past the post during an opening quarter in which Grimsby had the upper hand.
In response, Mike Flynn saw a shot blocked by Disley, while Pipe headed over from Andy Sandell's cross before the home side went in front.
Alex Gilbey picked up the ball in midfield and provided the pass for Jolley, who shot across the face of goal beyond the dive of McKeown.
The goal gave the home side confidence, Gilbey's effort from the edge of the box forcing McKeown into a save.
Grimsby introduced top scorer Andy Cook at half time in place of Shaun Pearson. But, rather than sit back on their lead, Newport continued to press forward, Flynn missing a glorious opportunity to settle the tie only to scuff the ball wide from close range.
Crow had a goal disallowed for offside and a Flynn shot was gathered at the second attempt by McKeown as Newport dominated.
The Mariners needed two goals to take the game into extra-time but they were not putting Pidgeley under any great pressure. And Edinburgh's side saw out the game comfortably to set up an all Welsh final at the home of English football on 5 May.
VIEW FROM THE DRESSING ROOM
Newport County scorer Christian Jolley told BBC Radio Wales:
"It's unbelievable, look at the atmosphere. The fans are buzzing, we're buzzing, we've had a great day.
"We kept a clean sheet against Grimsby in two legs and it's a great achievement.
"It's brilliant, I can't ask for more. I've been here since January permanently now and it's the icing on the cake.... you've seen us today, we were brilliant."
Grimsby Town joint manager Paul Hurst told BBC Radio Humberside:
"It's a long hard season. A lot of hard work goes in, you get to the play-offs, you know what the deal is, and we came up slightly short over the two games.
"I thought today that we started the game well, we've had three decent chances to get in front and then we missed a chance.
"Second half, especially towards the end of the game, they were always going to have a couple of chances and have gaps to play in because we were going to have to change it
"I'm just disappointed that second half we never really put them under any pressure."
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Live Text Commentary
Full Time The referee brings the game to a close.90:00 +3:01
Lenny Pidgeley handles the ball and concedes a free kick. Joe Colbeck crosses the ball from the free kick right-footed from left wing, clearance by David Pipe.90:00 +2:38
Robbie Willmott is ruled offside. James McKeown takes the indirect free kick.89:49
The ball is swung over by Joe Colbeck, save by Lenny Pidgeley.88:38
Short corner taken by Andy Sandell.87:53
Short corner taken by Andy Sandell. Short corner taken by Andy Sandell from the left by-line.86:33
Centre by Andy Sandell, Aswad Thomas makes a clearance. Robbie Willmott produces a left-footed shot from deep inside the penalty box which goes wide of the left-hand post.85:11 Substitution
Substitution Robbie Willmott comes on in place of Christian Jolley.83:04
Centre by Andy Sandell, blocked by Tom Naylor.81:57
Aaron O'Connor is penalised for handball and concedes a free kick. James McKeown takes the free kick.78:18
Free kick taken by Lenny Pidgeley.78:18 Booking
Booking Booking for Ross Hannah.78:12
Ross Hannah handles the ball and concedes a free kick.77:35
Christian Jolley produces a left-footed shot from inside the area that clears the bar.76:55
Effort from inside the area by Alex Gilbey misses to the left of the target.75:39
Christian Jolley is ruled offside. Indirect free kick taken by James McKeown.74:06
The assistant referee signals for offside against Aaron O'Connor. Indirect free kick taken by James McKeown.73:22
Free kick awarded for an unfair challenge on Aaron O'Connor by Andi Thanoj. Andy Sandell restarts play with the free kick.71:44 Substitution
Substitution Aaron O'Connor on for Danny Crow.70:29
The ball is swung over by Michael Flynn, comfortable save by James McKeown.
Substitution Sam Hatton goes off and Dayle Southwell comes on.67:37
Aswad Thomas produces a cross, Ismail Yakubu manages to make a clearance.65:55
Corner taken left-footed by Andy Sandell from the right by-line, Andi Thanoj manages to make a clearance.64:41
Short corner taken by Joe Colbeck.63:21 Substitution
Substitution Liam Hearn goes off and Ross Hannah comes on.62:09
Danny Crow challenges Aswad Thomas unfairly and gives away a free kick. James McKeown restarts play with the free kick.60:18
Michael Flynn concedes a free kick for a foul on Aswad Thomas. Direct free kick taken by James McKeown.57:52
Danny Crow produces a drilled right-footed shot from 20 yards. Marcus Marshall gets a block in. Michael Flynn takes a shot. Comfortable save by James McKeown.57:16
Andy Sandell crosses the ball, clearance by Aswad Thomas.56:06
The offside flag is raised against Danny Crow. James McKeown restarts play with the free kick.54:48
Centre by Marcus Marshall, Andy Cook takes a shot. Byron Anthony gets a block in. Corner taken right-footed by Joe Colbeck from the left by-line, Tony James manages to make a clearance.53:37
Michael Flynn produces a right-footed shot from close range which goes wide of the left-hand post.53:16
Christian Jolley crosses the ball, clearance by Tom Naylor.52:50
Centre by Christian Jolley, Craig Disley manages to make a clearance.49:50
Andy Cook is caught offside. Indirect free kick taken by Lenny Pidgeley.49:31
Christian Jolley challenges Sam Hatton unfairly and gives away a free kick. Sam Hatton restarts play with the free kick.45:48
Centre by Alex Gilbey.45:01
The referee blows his whistle to start the second half.45:01 Substitution
Substitution Andy Cook is brought on as a substitute for Shaun Pearson.45:00 +2:46 Half time
Half Time The players leave the pitch at half time.45:00 +2:26
The ball is swung over by Marcus Marshall, Liam Hearn produces a right-footed shot from deep inside the penalty area which goes wide of the left-hand post.45:00 +1:47
Danny Crow challenges Shaun Pearson unfairly and gives away a free kick. Direct free kick taken by Sam Hatton.42:55
Craig Disley has an effort at goal from just inside the box that misses to the left of the goal.42:29
Andy Sandell has an effort at goal from 20 yards. Lenny Pidgeley makes a comfortable save.42:05
Centre by Joe Colbeck.41:30
The ball is swung over by Joe Colbeck, Tony James manages to make a clearance.40:17
Andy Sandell sends in a cross, Shaun Pearson manages to make a clearance.39:42
Joe Colbeck is flagged offside by the assistant referee. Indirect free kick taken by Lenny Pidgeley.39:24
Marcus Marshall crosses the ball, Lee Minshull manages to make a clearance.39:13
The ball is delivered by Aswad Thomas, clearance made by Michael Flynn.35:26
Andy Sandell has a headed effort at goal from just inside the penalty area that misses to the left of the target.34:48
Tony James restarts play with the free kick.34:48 Booking
Booking Tom Naylor goes into the book for unsporting behaviour.34:42
Unfair challenge on Michael Flynn by Tom Naylor results in a free kick.34:24
Effort on goal by Alex Gilbey from 20 yards. Save made by James McKeown.33:18
Shot from deep inside the area by Christian Jolley clears the crossbar.31:26
Outswinging corner taken by Joe Colbeck from the right by-line, Headed effort from deep inside the area by Craig Disley misses to the left of the goal.30:09
Assist on the goal came from Alex Gilbey.30:09 Goal scored
Goal! - Christian Jolley - Newport 1 - 0 Grimsby Christian Jolley finds the net with a goal from the edge of the penalty box to the bottom left corner of the goal. Newport County 1 (2)-(0) 0 Grimsby.27:41
The ball is sent over by Alex Gilbey, Close range header by David Pipe goes wide of the left-hand post.26:23
Marcus Marshall is caught offside. Lenny Pidgeley takes the free kick.23:05
Andy Sandell takes the inswinging corner, clearance by Craig Disley.20:38
Shot from 18 yards by Michael Flynn. Blocked by Craig Disley.19:51
Lenny Pidgeley fouled by Shaun Pearson, the ref awards a free kick. Direct free kick taken by Lenny Pidgeley.19:14
Sam Hatton takes the direct free kick.19:14 Booking
Booking The referee cautions Alex Gilbey for unsporting behaviour.19:02
Alex Gilbey concedes a free kick for a foul on Craig Disley.16:30
Craig Disley produces a cross, comfortable save by Lenny Pidgeley.15:17
Joe Colbeck produces a cross, clearance by Michael Flynn.14:42
Tom Naylor takes a shot. Save by Lenny Pidgeley. Corner taken by Joe Colbeck from the right by-line to the near post, clearance made by David Pipe.14:05
Unfair challenge on Aswad Thomas by Michael Flynn results in a free kick. Sam Hatton takes the direct free kick.11:43
Unfair challenge on Christian Jolley by Sam Hatton results in a free kick. Free kick crossed right-footed by Michael Flynn from left wing, save by James McKeown. Corner taken by Andy Sandell, clearance made by Shaun Pearson.10:29
The ball is sent over by Marcus Marshall, clearance made by Ismail Yakubu.10:21
Sam Hatton sends in a cross.7:27
The ball is delivered by Joe Colbeck, clearance made by Michael Flynn.5:46
Effort from deep inside the area by Tom Naylor clears the bar.5:19
Alex Gilbey challenges Andi Thanoj unfairly and gives away a free kick. Direct free kick taken by Sam Hatton.3:25
The ball is delivered by Michael Flynn, Danny Crow produces a header from deep inside the six-yard box that clears the bar.0:21
Ismail Yakubu gives away a free kick for an unfair challenge on Marcus Marshall. Free kick crossed right-footed by Joe Colbeck from left wing, comfortable save by Lenny Pidgeley.0:00
The referee gets the game underway.
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