GRAHAM Dorrans' stunning 33rd-minute free-kick proved decisive as Albion made hard work of chalking up a fourth successive win.
The Baggies stormed into a two-goal lead inside the opening nine minutes thanks to Ben Watson's first goal for the club and Chris Brunt's 11th of the season.
Preston centre-half Sean St Ledger pulled one back on 15 before the hosts converted sustained pressure into a third goal, with Dorrans netting his 16th of the term from 30 yards.
Albion again failed to hold onto their two-goal advantage when former Liverpool striker Neil Mellor made it 3-2 two minutes before half-time.
But the hosts successfully negotiated the second half with few further alarms to end North End's five-game unbeaten run.
While Albion's mission today was all about cementing their place in the top two, Preston, who started the day in 13th, were aiming to close the seven-point gap on the final play-off place.
Ishmael Miller started on his own up front as Roberto Di Matteo rang two changes.
Powerhouse striker Miller replaced Luke Moore, who dropped to the bench, while Gianni Zuiverloon came in for the injured Jonas Olsson.
Jerome Thomas returned as a sub from a two-game hamstring injury absence.
Preston made two changes, with former Baggie Richard Chaplow and Michael Hart coming in for Billy Jones and Paul Coutts. Another ex-Hawthorns employee, Darren Carter, started on the bench.
Albion made the perfect start by storming into a two-goal lead - with the first two shots of the game!
In the seventh minute, Robert Koren's square-pass was inadvertently nudged into the path of Watson by St Ledger and the on-loan midfielder clinically clipped the ball past Andy Lonergan from 12 yards.
Just two minutes later, North End's attempted offside trap went horribly wrong as Dorrans slid the ball through to Brunt and the Northern Ireland international had all the time in world to slide it past the exposed Lonergan.
It was champagne football and it could have been 3-0 in the 13th minute when Dorrans turned Chris Sedgwick inside out before finding Miller, who headed a great chance well wide.
Scott Carson was called into action for the first time in the 15th minute when he pushed wide Sedgwick's downward header from Ross Wallace's cross.
However, it was to prove a momentary reprieve.
From Wallace's ensuing corner, St Ledger was allowed to ghost into the six-yard box totally unmarked and head home.
Preston's goal changed the flow of the game and the Baggies box was bombarded with set-pieces, the most dangerous of which - a Wallace free-kick - was pushed away at full stretch by Carson.
But Albion weathered the pressure and were soon back on the front foot.
On 25, forceful play by Watson allowed Brunt to whip a sublime centre into the six-yard box and only St Ledger's dynamic clearance under his own bar denied Miller a tap-in.
Three minutes later, Miller spun past Liam Chilvers and pulled the ball back for Brunt, who stabbed just wide at the near post.
Patient Albion play then set up a shooting chance for Koren, but his deflected 20-yard effort was saved low to his left by Lonergan.
However, the Preston keeper could do nothing Albion's third on 33, which had been coming.
Dorrans curled a sublime 30-yard free-kick towards the top right-hand corner and although Lonergan got his finger-tips to it, he didn't come close to keeping out a real goal-of-the-season contender.
The Albion pressure continued when Koren powered a 25-yard volley just over.
The hosts were completely in control - but more slack defending saw them pegged back again two minutes before the break.
This time it was the Albion offside trap which self-destructed, with Mellor being given the freedom of the park to race onto Wallace's ball and coolly round Carson before slotting home.
Preston threatened first after the interval when Carson had to be on his toes to push away Chaplow's 25-yard free-kick.
This had turned into a tense affair and Albion hit back on 57 with a miscued Brunt free-kick which crept under the North End wall and into Lonergan's grasp.
The action swung to the other end but Mellor could only direct a weak header straight at Carson from Callum Davidson's angled centre.
But Albion were still playing some exquisite stuff and after Gabriel Tamas found Koren with a sublime cross-field ball, the Slovenian set up Watson, whose instinctive 15-yard volley was pushed away by Lonergan.
From Brunt's ensuing corner, it took a frantic goalline clearance by Mellor to prevent Tamas' far-post header going in.
Albion were turning the screw now and Miller raced onto Koren's lay-off before twice seeing angled drives from inside the box blocked by the excellent Lonergan
Another chance went begging when sub Moore brilliantly powered past Chilvers and saw his low cross blasted over by the off-balance Dorrans at the far post.
But ultimately Albion didn't need a fourth goal to seal three more vital points as Preston's wait for a Hawthorns win stretched to almost 37 years.
ALBION (4-5-1): Carson; Zuiverloon, Meite, Tamas, Cech; Koren (Barnes 65), Watson, Mulumbu, Dorrans, Brunt (Morrison 87); Miller (Moore 72). Subs not used: Kiely (gk), Thomas, Cox, Mattock.
PRESTON (4-4-2): Lonergan; Hart, Chilvers, St Ledger, Davidson; Sedgwick (Treacy 83), Chaplow, James, Wallace; Brown (Parkin 83), Mellor. Subs not used: Henderson (gk), Collins, Carter, Barton, Miller.
GOALS: ALBION - Watson (7), Brunt (9), Dorrans (33). PRESTON - Sedgwick (15), Mellor (43.
BOOKINGS: ALBION - Meite (foul 51). PRESTON - Sedgwick (foul 36), Chaplow (foul 73), Chilvers (foul 80).
REFEREE: J Singh (Middlesex).
ALBION STARMAN: Ben Watson.