Saracens - Tries: Martinez Gion, Clapp, Mackinder, Botterman Cons: Rowland 2 . Harlequins - Tries: Myers, Breach, McCormack Cons: Green Pens: Green.
Saracens were ahead in the opening five minutes as Sam Martinez Gion gathered from Hannah Botterman's break to crash over, before Harlequins responded through the boot of Ellie Green for their first points.
27' HAR 3 - 10 SAR— Tyrrells Premier 15s (@Premier15s) April 29, 2018
CAPTAIN FANTASTIC 👊 @saracenswomen skipper @lotteclapp slices through the Quins defence and scores ⚡
Watch the #Premier15sFinal LIVE on @skysports or on https://t.co/CWGtvVEgYP pic.twitter.com/AP97isqtGd
As Sarries dominated territory and possession they were rewarded when captain Charlotte Clapp hit a superb line back inside from Zoe Harrison's pass, to race in under the posts from just outside the 22.
On the stroke of half-time Saracens got their third score when wing Garnet Mackinder bounced out of a tackle and finished well, before Quins' first meaningful spell of pressure saw Holly Myers go over out wide as it sat 17-8 at the break.
Harlequins continued that momentum gained at the start of the second half when replacement Jess Breach took a quick tap and go from five metres out to dive over, her 17th score of the season.
46' HAR 8 - 17 SAR— Tyrrells Premier 15s (@Premier15s) April 29, 2018
TAP AND GO 🔥 @HarlequinsWomen take a quick pen and score in the corner to narrow the deficit just before the break.
Watch the #Premier15sFinal LIVE on @skysports or on https://t.co/CWGtvVEgYP pic.twitter.com/jL3eGN2t1D
Helena Rowland's superb break eventually led to Botterman going over as Saracens got their fourth try but again Quins came back to bring the game to within four points with 10 minutes remaining.
With Poppy Cleall sent to the sin bin for Sarries, Quins pressed late on but Saracens, who finished top of the table before the play-off semi-finals, held on to clinch the title.
In the two previous meetings between the teams this season both had won one game, with Saracens winning 28-19 at Twickenham Stoop and Harlequins victorious 32-29 in the final round of the season at Allianz Park.
The final proved to be another tight affair between the best two teams in the country, as the match ebbed and flowed with both enjoying spells on top.
Despite Saracens scoring the first three tries of the game, Quins' impressive resurgence that started in time added on at the end of the first half meant they were always in touch.
Saracens pack has been the cornerstone of their success this season and it was their impressive work in the tight that set up the foundations for the team to work from.
England pair Poppy Cleall and Marlie Packer, along with Bryony Cleall, were consistently carrying over the gainline through heavy traffic as the Sarries back row stamped their authority on the game.
Both Sarries props got on the scoresheet as Martinez Gion and Botterman were part of a whole pack effort that put in an impressive shift.
Saracens captain Charlotte Clapp: "I'm over the moon, I can't explain it. That last 30 seconds my feelings were all over the place, I'm so proud of everyone.
"It just kept going back and forth, Harlequins kept getting momentum and we just had to stick to it and empty the tank.
"It's so nice when you're doing things on the training ground and you pull it off (for the try) but it was a whole team effort."
Harlequins Ladies joint head coach Gary Street: "We're very disappointed as I thought we should have won. I thought over the 80 minutes we were the best side.
"It was good for the game as this was a good avert for our sport. Hopefully we can now take it to another level next year."
Harlequins Ladies: 15. Jess Wooden, 14. Holly Myers, 13. Fiona Pocock, 12. Rachael Burford (c), 11. Natasha Bradshaw, 10. Ellie Green, 9. Leanne Riley; 1. Vickii Cornborough, 2. Davinia Catlin, 3. Chloe Edwards, 4. Abbie Scott, 5. Zoe Saynor, 6. Shaunagh Brown, 7. Deborah McCormack, 8. Fiona Fletcher.
Replacements: 16. Tove Viksten, 17. Ashleigh Greenslade, 18. Alex Hardy, 19. Samantha McCarthy, 20. Bobbie Haywood, 21. Jess Breach, 22. Stacey White
Saracens Women: 15. Nina Vistisen, 14. Garnet Mackinder, 13. Lauren Cattell, 12. Helena Rowland, 11. Lotte Clapp (c), 10. Zoe Harrison, 9. Georgie Gulliver; 1.Hannah Botterman, 2. Kat Evans, 3. Sam Martinez Gion, 4. Sonia Green, 5. Tess Wijmans, 6. Bryony Cleall, 7. Marlie Packer, 8. Poppy Cleall.
Replacements: 16. May Campbell, 17. Sarah Barber, 18. Rosie Galligan, 19. Valeria Fedrighi, 20. Ella Wyrwas, 21. Cara Wardle, 22. Emma Uren