Carlisle United went close with a late fight back but it wasn't quite enough as Plymouth protected their winning streak to bring an end to the visiting run of three consecutive league victories.
Bolton loanee Georg Iliev made his debut having signed just 24 hours earlier with fellow Trotter Hayden White at right back as he heads into a second month with the club.
Carlisle started well but a Thirlwell free kick, flicked on by Iliev, was cleared long by McCormick. Reuben Reid was in acres of space and his cut back put it on a plate for Alessandra. It was a firm connection but White held his position to make a vital block as the ball headed for the back of the net.
A carbon copy break just seconds later again found Reid with time on his hands. He stepped past Brough but his toe poke across the face of goal evaded everybody.
Carlisle worked hard to close the gaps and they got forward well on 10 minutes when Dempsey found White on the right flank. His deep cross had Beck interested until Nelson jumped to clip it away.
The hosts had concentrated on the United left flank but they broke the deadlock with a slick move down the right hand side with Hartley and Blizzard in close attendance. Reuben Reid had an initial volley blocked but Alessandra was on hand to sweep the pieces into the roof of the net.
Plymouth suddenly looked dangerous and O'Connor left Brough for dead when he turned inside tight by the corner flag. He went for glory and Thirlwell did enough to deflect it away to safety.
A dangerous free kick delivery caused more problems for United as Hartley twisted and turned to make it his inside the six yard box. He lost the flight of the ball and was disappointed as he allowed it to run through to the keeper.
A run of corners followed for the Pilgrims and Alessandra had to be stopped in his tracks by White as a half clearance was played into his path. The tackle was perfect as the striker's eyes lit up.
United fashioned a decent opening on 38 minutes when Dempsey wriggled away from his man. Nelson got a toe to the drive and McCormick was able to grab the deflected shot as it dropped out of the air.
Alessandra received the wrath of his team mates when he was played clean through by Blizzard. Reid was in space but, caught in two minds, he opted for a weak shot which Hanford was able to grasp.
Carlisle saw more of the ball in the midfield areas and a 24 yard shot from Potts suggested they could find a route back into the game. He caught it well but it was always heading wide.
It was a better spell for the visitors and Dempsey sent White on a run with an accurate crossfield pass. The near post cross was well struck but Beck couldn’t quite make up the ground.
The second half started at a slower pace, as Robson and O'Hanlon replaced Symington and Thirlwell for United, but Plymouth went close when Bobby Reid took charge of a 24 yard free kick. His dipping strike beat the wall and shaved the outside of the post as he held his head in his hands.
A positive run from White brought yellow shirts up in support and his rolled pass across the face of goal handed Iliev a chance to shoot. He caught it on the spin but he couldn't keep it down.
A deep Dempsey corner brought a neat nod down from Beck as Carlisle stayed forward but O'Hanlon couldn't get enough on it to trouble the keeper as he poked it through a gaggle of legs.
Substitute Deane Smalley smashed a shot right at Hanford moments after he came on and Bobby Reid pulled on wide as the Pilgrims imposed themselves on proceedings once more.
Smalley used his pace to release Alessandra as the Pilgrims asked late questions and Hanford had to be firm once more as it swirled and moved in front of him.
United thought they'd equalised when a late corner was met on the full by Archibald-Henville, The keeper was beaten but Nelson was there to head away off the line. Robson kept his eye on the clearance and his volley, which also had McCormick beaten, was stopped by McHugh as he stepped across to protect the goal.
A flick from Beck gave Iliev another late chance but McCormick did enough to get in the way as the new man, and substitute Stephen Elliott, battled away to try to get the ball over the line.
Plymouth - Alessandra (15)
United - Archibald-Henville (20), White (88)
Plymouth Argyle - McCormick, Nelson, McHugh, Hartley, O'Connor, Cox, B Reid, Blizzard, Mellor, Alessandra (Morgan 90), R Reid (Smalley 73). Subs - Bittner, Norburn, Banton, Kellett, Harvey.
Carlisle United - Hanford, White, Archibald-Henville, Thirlwell (O'Hanlon 46), Brough, Symington (Robson 46), Dicker, Dempsey (Elliott 86), Potts, Beck, Iliev. Subs - Caig, Marrow, Sweeney, Gillies.
Referee - Mr Patrick Miller
Attendance - 6,529 (193 away fans)