YASSINE El Ghanassy grabbed his second Barclays Under 21 Premier League goal of the season as Albion secured a 1-0 victory over the Gunners at The Hawthorns.
All the pre-match hype concerned Arsenal and England midfielder Jack Wilshere, who started his first competitive game in 16 months, after recovering from a foot injury.
But the Baggies earned their first win since the opening day of the season with a solid defensive display – sparked by the attacking flair of El Ghanassy.
Development coach David Oldfield made four changes to the side that lost 1-0 at Norwich ten days ago - with Kayelden Brown, Saido Berahino, Scott Allan and Adil Nabi
making way for Isaiah Brown, Romaine Sawyers, Mani O’Sullivan and El Ghanassy.
Arsenal started the brighter of the two sides and would have been ahead inside six minutes had Shane Lewis not been on hand to tip over Kyle Ebecilo’s right-foot strike from 20 yards.
Wilshere dissected the Baggies defence on 17 when his throughball found Nigel Neita in space ten yards from goal.
Lewis could only parry Neita’s left-foot effort and Liam O’Neil’s excellent goalline block denied Josh Rees from the rebound.
Sam Mantom’s right-foot shot from 25 yards provided Albion’s first strike at goal in the 22nd-minute - but Emiliano Martinez gathered comfortably in the Arsenal goal.
Ebecilo had another fine opportunity to put Arsenal ahead on 25 but was denied by a last-ditch block from Donervorn Daniels after a clever one-two with Emmanuel Frimpong.
El Ghanassy came close for the Baggies when his 36th-minute free-kick whistled just wide of the right-hand post from 22 yards.
But the Belgium international grabbed his goal four minutes later - slotting home George Thorne’s deadly throughball with his right foot from 12 yards.
The on-loan attacker should have doubled Albion’s lead three minutes later but struck tamely into the arms of Martinez after dispossessing Frimpong on the edge of the area.
Daniels nearly extended the Baggies’ lead three minutes after the restart but his header struck the woodwork and went over from El Ghanassy’s corner.
The second half was somewhat subdued, with a host of substitutions contributing to the stop-start pattern of the game.
Wilshere signed off on a successful return to action when he was replaced by Kris Olsson after 63 minutes – while Frimpong bowed out on 70 with Serge Gnabry taking his place.
Sawyers directed a right-foot effort directly at Martinez on 85 with substitute Aaron Birch providing the opportunity after some positive football in midfield.
Arsenal responded immediately but Thomas Eisfeld sent his strike over the bar and into the Smethwick End from 20 yards.
And the woodwork saved the day for Oldfield’s men with Gnabry’s right-foot rocket striking the upright in the fifth minute of added time.
ALBION (4-2-3-1): Lewis; O’Neill, D Daniels, Gayle, Garmston; Mantom, Thorne; O’Sullivan, El Ghanassy (A Jones 81), I Brown (Birch 77); Sawyers. Subs not used: Palmer (gk); C Jones, S Nabi.
ARSENAL (4-5-1): Martinez; Bellerin, Hajrovic, Miquel, Meade; Rees, Wilshere (Olsson 63), Yennaris, Frimpong (Gnabry 70), Ebecilo; Neita (Eisfeld 75). Subs not used: Charles-Cook, Monteiro.
GOALS: Albion – El Ghanassy (40).
BOOKINGS: Arsenal – Martinez (90+2).
REFEREE: A Hendley (West Midlands)
ALBION STARMAN: Yassine El Ghanassy
PIC: STAR ATTRACTION...Albion's Isaiah Brown challenges Jack Wilshere