Sale Sharks recovered from a slow start to overpower under-strength Scarlets, with Danny Cipriani claiming 21 points.
The former England fly half scored a try, four penalties and two conversions with other tries from Richie Vernon, Charlie Amesbury and Charlie Ingle.
Scarlets led 14-3 early on after tries by Andy Fenby and Gareth Davies, both converted by Owen Williams who also kicked a penalty.
The win means Sharks top Pool 2 in the LV= Cup by a point from Leicester.
Sale Sharks: Cameron Shepherd, Rob Miller, Johnny Leota, Sam Tuitupou, Charlie Amesbury, Danny Cipriani, Dwayne Peel; Alasdair Dickinson, Marc Jones, Tony Buckley, Kearnan Myall, Tom Holmes, Dan Braid, David Seymour (Captain), Richie Vernon
Replacements: Tommy Taylor, Ross Harrison, Henry Thomas, Fraser McKenzie, James Doyle, Will Cliff, Jordan Davies, Charlie Ingall
Scarlets: Gareth Owen, Kristian Phillips, Gareth Maule (capt), Adam Warren, Andy Fenby, Owen Williams, Gareth Davies, Rhodri Jones, Emyr Phillips, Deacon Manu, Jake Ball, Johan Synman, Lewis Rawlins, Duane Eager, Kieran Murphy
Replacements: Kirby Myhill, Rob Evans, Peter Edwards, Richard Kelly, Tomas Vallejos, Aled Davies, Nick Reynolds, Dale Ford.