MAREK Cech's brilliant double fired unbeaten Albion back to the Coca-Cola Championship summit.
The former Porto ace whistled a stunning 25-yard drive into the top corner to nudge the Baggies 2-1 up five minutes before the break.
Only six minutes earlier, Shelton Martis had scrambled home Albion's first to cancel out Jamie Mackie's 12th-minute opener.
Cech had failed to notch in 17 previous outings for the club but helped himself to a second four minutes from time to seal struggling Plymouth's fifth defeat in six games.
Roberto Di Matteo's side were made to work for their sixth win in seven matches but were full value for the victory.
Simon Cox was handed his full league debut in place of Luke Moore (ankle) in attack.
Fit-again duo Chris Brunt and Gianni Zuiverloon plus Graham Dorrans also returned, with Robert Koren, Jerome Thomas and former loan signing Shaun Cummings making way.
Albion produced the first meaningful moment in the fifth minute when Roman Bednar, making his first home league appearance of the term, raced onto Brunt's disguised reverse ball and saw his vicious centre fly just in front of Cox, who was lurking in the six-yard box.
Plymouth's game-plan was to keep plenty of men behind the ball and try to hit the hosts on the counter-attack and it was Albion who threatened again on 12 when Zuiverloon fired just wide from 25 yards.
But it was Argyle who drew first blood within the same minute.
Mackie out-muscled Martis to race onto Alan Gow's ball over the top before firing under Scott Carson from a tight angle, with the effort just squirming over the goalline.
Albion weren't short on effort but were struggling for rhythm as the visitors continued to frustrate them.
And the Baggies, who had looked indecisive at the back, had a huge let off in the 22nd minute when Gary Sawyer failed to hit the target with a free header from Karl Duguid's right-wing centre.
Albion were soon back on the attack and Bednar will feel he should at least have tested Plymouth keeper Romain Larrieu with a free header from Dorrans' corner which ballooned high into the Smethwick End.
Di Matteo's men were gradually getting back on top and Cox was inches away from restoring parity with a first-time, 20-yard drive from Zuiverloon's pinpoint square ball.
Brunt almost squeezed an opening for Cech on the half-hour mark but the Slovakian international took one touch too many, allowing Larrieu to steal the ball off his toes.
The Baggies had now built up a terrific head of steam and Plymouth finally caved in in the 34th minute.
Jonas Olsson towered at the near post to head Dorrans' corner goalwards and central-defensive partner Martis had the simple task of smashing his second goal of the season home from a yard.
Albion were brimming with confidence and a terrific move involving Cox and Zuiverloon should have led to a second goal four minutes later.
However, Cech lost his balance as he shaped to shoot and his mishit effort looped just wide of Larrieu's despairing dive - and the left-hand post.
Bednar was the next to threaten when he controlled Brunt's ball over the top and volleyed wide.
Plymouth suffered an injury setback when giant defender Reda Johnson limped off and was replaced by Chris Clark - and it went from bad to worse for the Pilgrims on 40.
Cech got The Hawthorns on its feet with a dipping 25-yard drive which looped over Larrieu and into the far top corner of the net. Bednar had created the shooting opportunity by chesting down Martis' ball.
The Albion siege continued right up until the half-time whistle and Zuiverloon was inches away from adding a third with a ferocious 15-yard drive.
In truth, the angle was always against the right-back and he would have been better served crossing to a team-mate.
The only change at half-time was the visitors' shirts, with the Pilgrims switching from white to green at the request of boss Paul Sturrock.
Albion thought they had a two-goal cushion three minutes after the break when Cech raced onto Martis' exquisite 50-yard throughball and slotted past Larrieu - but the effort was ruled out for offside.
The Baggies were really turning the screw now and Bednar fired inches over from just inside the box after forceful play by Cech and Brunt.
But Plymouth almost equalised with a 52nd-minute bolt out of the blue.
Steve MacLean headed a deep left-wing centre back into the danger-zone and everyone stood and watched as Mackie's first-time shot cannoned off the underside of the bar before Albion scrambled the ball to safety.
Back came the Baggies and it took a wonderful save at full stretch from Larrieu to turn Dorrans' 20-yard drive around his near post.
Albion were playing some delightful stuff and Plymouth were having to dig deep, and put their bodies on the line, to repel the Baggies' attacks.
But while the advantage remained at a solitary goal, the hosts couldn't afford to take their foot off the gas.
That point was underlined when sub Krisztian Timar headed wide from Carl Fletcher's free-kick, although Carson had the effort covered.
And captain Carson had to pull off a stunning one-handed save seven minutes from time to prevent Clark's header looping in from another Fletcher set-piece.
But Cech put the result beyond doubt four minutes from time with a textbook downward header from Dorrans' centre.
Incredibly, Cech should have been celebrating a hat-trick in the final minute.
Sub Chris Wood took on the Plymouth defence single-handedly and did well to prod the ball to the left-midfielder, who fired wastefully over from 12 yards.
But that failed to take the gloss off a fine individual performance by Cech, who was narrowly beaten to the man-of-the-match award by the once-again impressive Dorrans.
ALBION (4-4-2): Carson; Zuiverloon, Martis, Olsson, Mattock; Brunt (Thomas 78), Mulumbu, Dorrans, Cech; Bednar (Wood 70), Cox (Koren 62). Subs not used: Kiely (gk), Barnett, Reid, Teixeira.
PLYMOUTH (5-3-2): Larrieu; Duguid, Arnason, Fletcher, Johnson (Clark 38), Sawyer; Summerfield (Sheridan 66), MacLean (Timar 66), Gow; Mackie, Paterson. Subs not used: Letheren (gk), Fallon, Judge, Wright-Phillips.
GOALS: ALBION - Martis (34), Cech (40, 86). PLYMOUTH - Mackie (12).
BOOKINGS: ALBION - Dorrans (simulation 82).
REFEREE: G Salisbury (Lancashire).
ALBION STARMAN: Graham Dorrans.