A week on from their league defeat to the Devon side, Bournemouth led early on and held on for the majority of the 90 minutes to claim the cup.
Helen Bleazard’s side led by a goal at the interval after a tight first half, as Kenni Thompson scored direct from a corner in the opening minutes to give Bournemouth the advantage.
The second half was also an even affair, as Plymouth became increasingly desperate to draw themselves level.
But Bournemouth defended resolutely and held on to secure the cup.
Bleazard named an unchanged team from the side that started the defeat to Argyle last weekend.
The Cherries were out for revenge after that result, and they made a fast start.
Elena Cole rattled the crossbar from 30 yards as she forced Hermione Cull to tip the ball onto the crossbar, before the Cherries took the lead.
Jenna Markham. (Image: Antony Roveschi)
It was a brilliant Olimpico from Thompson as she swung her corner into the danger area, it beat everyone and dropped into the net at the far post with six minutes on the clock.
Plymouth’s first attempt of the game came in the tenth minute as Katie Wilson fired towards goal, but it was at a comfortable height for Katie Scadding to catch in the Cherries goal.
Sophie Quirk tested Cull with a free kick from the left of the box, right on the edge of the area, but she saved and Plymouth were able to clear after a scramble in the six-yard box.
Quirk fired wide with her next attempt, before Phoebie Poole tested Scadding, but again it was at a good height for the keeper to catch.
Jessica Hennessy (Image: Antony Roveschi)
Plymouth were being limited to shots from range and skipper Roisin Kivel was the next to try, but her shot flew well over the bar.
Poole had another go but shot off target from outside of the box, before a good save from Cull denied Quirk on the angle to keep the deficit at one.
A Charlotte Harris long throw caused the Pilgrims some problems in first half stoppage-time, but they were able to clear and the Cherries led at the break.
It was a very even start to the second half, with few openings for either side in the opening ten minutes of the half.
Quirk had the first effort on goal of the half that was straight at Cull, before the Cherries forward was not far away from a good ball in from Kelci Bowers.
Elena Cole (Image: Antony Roveschi)
Plymouth had the ballin the back of the net in the 66th minute, as Poole touched home after a Tamara Wilcock strike from a corner routine, but the flag went up for offside.
Bleazard went to her bench with 22 minutes to play, as Molly Barron-Clark and Freya Meadows Tuson came on for goalscorer Thompson and Georgia Wilson.
Scadding did brilliantly to get down and palm an Olivia Francis cross away from goal as two Plymouth players waited to tap in at the back post.
The Cherries went close to doubling their advantage when a Quirk cross took a heavy deflection off Katie Wilson and wrongfooted Cull, but the keeper readjusted and caught well.
Kelci Bowers (Image: Antony Roveschi)
Phoebe Williams was introduced by Bleazard with 14 minutes to play, as she replaced Elena Cole.
Plymouth hit the post when Noble met a cross from the right but the Cherries survived, before James hooked a cross away from danger in the six-yard box.
It was scrappy as Plymouth sought to create a final chance to draw themselves level, with Scadding imperious as she caught a free kick well and punched a cross away from the Plymouth forwards.
An Argyle corner dropped onto the roof of the net before Wilson fired over the bar from the top of the box in what was the final chance of the 90 minutes and the Cherries held on to win the National League Cup.
They will now hope to use the cup win to build momentum and chase down Argyle and Watford to secure promotion to the WSL2 in the remainder of the season.