In the winner-takes-all decider, Alan Jackson put Fylde ahead right on the stroke of half-time.
In the second half two goals from Joe Booth and late strikes from substitutes Glenn Steel and Matt Walwyn sealed a convincing win.
The result means the club will play in the Unibond League North next season with a number of 'Lancashire derbies' to look forward to.
In the second minute Fylde keeper Nathan Worrell was deceived by a free-kick from Carlos Meakin that bounced awkwardly in front of him and hit him on the chest before being cleared to safety.
At the other end, a fine solo run from Richie Allen saw him beat two men on the edge of the box before firing in a shot that was well held by Millers' keeper Liam Higginbotham.
The tempo was raised in the closing minutes of the first half, with chances created at both ends. A minute from half-time Fylde got the breakthrough they needed, when a great run by Richie Allen down the left saw him hit the byline and cut the ball back into the path of Alan Jackson, who rifled a low shot under the keeper to grab the opening goal.
In the opening stages of the second half Fylde began to enjoy the better of the possession, with Richie Allen involved in most of his side's best attacking moves.
But as the game reached the midway point, it turned firmly in Fylde's favour when Micky Horsfall fired a cross in that hit New Mills defender Danny Jackson on the arm, and the referee had no hesitation in pointing to the spot. Joe Booth stepped up and tucked the ball low into the right-hand corner of the net - a 100% record from the penalty spot for the goalscoring midfielder.
Straight from the restart, New Mills had another good chance when Adam Morning's free kick was cleared only as far as Craig Marsh, who fired a shot into the side netting.
From then on, Fylde took control and Richie Allen, Mark Wane and Chris Downey all missed chances before New Mills' afternoon got worse with 11 minutes remaining, when centre half Mike Ryan was red carded for an off-the-ball incident.
Eight minutes from time, Fylde put the game out of reach when Mark Wane set up an easy chance for substitute Glenn Steel to side foot home the third goal from close range.
Two minutes from time, a neat passing movement between Joe Booth and Chris Downey ended with Booth firing a low shot across the keeper and into the far corner for his second and Fylde's fourth goal.

But there was still time for last season's Wembley hero Matt Walwyn to get in on the act, as the game moved into stoppage time. After taking up a left-wing position when he entered the field, Walwyn chased a long ball down the middle when play restarted, and when New Mills keeper Higginbotham was deceived by the bounce of the ball, Walwyn nipped in to roll the ball into the empty net for the fifth goal - cue the celebrations.
1217 witnessed Fylde's last day title clincher - a club record crowd and club officials will hope that kind of support will be back to watch them next season in Step 4 of the football pyramid.
Richie Allen was selected as the Match Sponsors CMYK Group as the man of the match.
Both teams were presented with their medals and Fylde celebrated in style!

Team: Worrell, Jackson, Moran, Shaw, Thompson, Palmer, Booth, Allen, Horsfall, Wane, Downey Subs: Walwyn,Steele, Blackwell, Lawlor, Watt