Uwe Rosler’s men built on their 1-0 win at the Proact last month to do the double over Danny Wilson’s men as Chesterfield slipped to their eighth successive league defeat.
Town took the lead in the 26th minute as David Ball fizzed the ball across to Bell at the back post who smashed the ball home.
The hosts wasted numerous chances to increase their lead but Nirennold made it 2-0 just minutes after entering the fray as he diverted Ash Hunter’s cross home unmarked at the back stick.
It should have been plain sailing for Town from that point on but as the torrential rain began to pour Town’s passage to three points was rocked by a Jay O’Shea penalty.
Ball had tripped Kristian Dennis in the box and O’Shea lifted the ball over ex-Spireites keeper Alex Cairns in the 66th minute.
Despite some late scares Town held on to pick up the win and move up to 11th in the League One table.
Town boss Rosler made three changes to the side that beat Southport 4-1 after extra-time in their FA Cup first round replay on Tuesday night.
Cairns kept his place in goal to make his first ever league start and only his second appearance of the campaign.
His first was in Town’s 1-0 win at Chesterfield after Chris Neal sustained a head injury and Rosler decided to give the keeper a start against his old club.
Conor McLaughlin returned from international duty to slot into a new 3-5-2 wing back formation as a right wing back as he replaced Nirennold.
Ash Hunter and Cian Bolger also returned to the starting line-up with Aaron Amadi-Holloway and Devante Cole moving to the bench.
Fleetwood made a roaring start with the new 3-5-2 wing-back formation allowing both Bell and McLaughlin to get forward and attack.
And the wing-backs were involved in a number of early chances.
Firstly McLaughlin nodded Grant’s ball from the left of the box straight at Allison before whipping the ball over to Bell at the left post but his close range effort was just saved by Allison.
Demsey rifled a set-piece from the edge of the box just wide of the left stick.
But despite Town’s dominance it was Chesterfield who should have taken the lead after a slip-up from Town keeper Cairns on his first ever league start.
The keeper spilled Donohue’s effort straight to John O’Shea and with Cairns floored it looked like Chesterfield would take the lead but O’Shea failed to even hit the target as he blasted the ball over the bar.
Ashley Eastham wasted a free-header but Town finally took the lead in the 26th minute.
Town striker David Ball produced a neat bit of skill with his back to goal to out-fox the Chesterfield defence and race to the back line before fizzing the ball across the six-yard box where Amari’i Bell swept home.
A long range Grant left-footed special just flew over the bar and Bell made a fine defensive
Allison slipped up on a back pass allowing Hunter in but the forward curled the ball wide of the right stick rather than squaring to the unmarked Ball who was in a better position.
The young forward did tee-up his strike partner as the half drew to a close but Ball nodded wide of the left stick.
A neat short-corner routine by Glendon saw him slide the ball to the unmarked Bell just inside the box but his fierce effort was blocked and Bolger nodded a free-header wide after Town had re-worked the ball outside the box with Grant teeing him up.
Bolger was booked by the referee and was brought off by Rosler minutes later with McLaughlin moving into the defensive three at the back and Nirennold deployed as right wing back.
Town orchestrated another slick counter-attack as Grant cut through the Spireites before teeing-up Ball but the striker’s delightful touch just flew the wrong side of the left post.
Nirennold finally made it 2-0 in the 66th minute as he used his long legs to divert in Hunter’s cross at the back post.
Town looked to be cruising to a comfortable win over a sorry Chesterfield side but they shot themselves in the foot as they gave away yet another penalty.
From nowhere Chesterfield found themselves back in the game after Dennis was tripped by striker Ball in the box allowing O’Shea to step up and fire home from the spot.
The goal woke Chesterfield up and some brave defending and good saves by Cairns kept Town in the game as they managed to stop Danny Wilson’s men from finding a way through.
Town always looked a danger on the counter with Cole sliding the ball to Hunter in the box but his effort was blocked
Rosler switched into a 4-4-2 formation with McLaughlin and Bell moving in to their usual full-back positions and Nirennold moving into the midfield.
Cole’s angled effort was just tipped away by Allinson’s fingers and O’shea wasted a great opportunity to level with Town substitute Aaron Amadi-Holloway squandering a late chance to put the game to bed.
But Town bagged the three points and their second win in a row after their FA Cup victory and climbed up the table into 11th.
Fleetwood team to face Chesterfield: Cairns, McLaughlin, Eastham, Pond, Bolger (Nirennold, 54), Dempsey, Glendon, Grant, Ball (Cole, 72), Hunter. Subs: Neal, Jonsson, Amadi-Holloway, Sowerby, Godswill, Cole.
Chesterfield: Allinson, Liddle, Evatt, Mitchell, O’Neill, Dimaio, Donohue, Dennis (Beesley, 72), Anderson, O’Shea, Ayiribi. Subs: Fulton, Simons, Humphreys, Maguire, Ofoegbu, German.
Referee: S Stockbridge.