ALBION gave Roy Hodgson a fitting send-off at The Hawthorns - but were unable to provide a positive result in a final-day five-goal thriller against the Gunners to put the gloss on it.
Marton Fulop - in for the injured Ben Foster - had a Baggies league debut to forget as he gifted Arsene Wenger's Champions League-chasing side two goals.
The Hungarian goalkeeper's mistake allowed Yossi Benayoun to notch a simple fourth-minute opener.
But team-mates Shane Long and Graham Dorrans got him out of jail with goals in the 12th and 15th minutes respectively.
Andre Santos levelled on the half-hour mark to make the scores level at the break.
And that is the way it would have stayed had Fulop's blunder from Robin van Persie's corner not presented Laurent Koscielny with the chance to grab what proved to be a 55th-minute winner.
A sell-out Hawthorns was awash with England flags and shirts in honour of departing boss Hodgson as the new national team manager took charge of the Baggies for the last time in a phenomenal 15-month reign.
Amidst the party atmosphere, Simon Cox and James Morrison were drafted into the starting XI in place of the absent Chris Brunt (tonsils) and the benched Keith Andrews.
Albion were also dealt a further blow with Foster's hopes of completing every minute of this Barclays Premier League campaign being ended by a groin injury in training yesterday.
Fulop was therefore handed his top-flight debut for the Baggies.
But he made the worst possible start as he dallied on the edge of his box following a challenge between Morrison and van Persie and allowed Yossi Benayoun to pinch the ball from him and roll it into the empty net to give the Gunners a fourth-minute lead.
The Baggies bounced back quickly and on five Marc-Antoine Fortune burst past Santos in the box and forced Wojciech Szczesny into a low save at the base of his near post.
Seven minutes later the hosts were level as Long burst clear onto Morrison's slide-rule pass and kept his cool to slot the ball past Szczesny and into the bottom left-hand corner of the net from just inside the box.
The game turned on its head in the 15th minute as Dorrans cleverly nodded Morrison's long diagonal pass past Koscielny and hit an unstoppable 20-yard volley past Szczessny to put the Baggies in front.
Benayoun could have levelled on 19 - but he volleyed Carl Jenkisnon's right-wing cross high and wide from 12 yards.
Jonas Olsson was then at full stretch to block in-form van Persie's goalbound strike from just outside the area.
Benayoun was presented with an even better chance to level on 25 as he found himself in space from Jenkinson's back-post cross - but was quickly closed down by Billy Jones and Gareth McAuley, who between them blocked his shot and cleared the danger.
The Gunners did level five minutes later as Alex Song dispossessed Youssouf Mulumbu and Santos pounced on the loose ball before skipping past Cox and seeing his 25-yard drive tipped onto the post by Fulop and in.
Arsenal skipper van Persie was perhaps a little lucky to see yellow instead of red seven minutes before the break as he clattered McAuley long after the Northern Ireland international had cleared the ball.
The Baggies were appealing for a penalty in first-half stoppage time as Cox's cross-cum-shot appeared to strike Francis Coquelin on the hand.
But referee Mike Jones swiftly waved play on.
The visitors launched a quick counter-attack, which resulted in Gervinho beating Liam Ridgewell in the box before drilling a shot into the side-netting to leave the scores level at the break.
Arsene Wenger made a change at the interval as Theo Walcott came on for Tomas Rosicky.
The Baggies were forced into a change of their own when Morrison limped off in the 50th minute following a robust challenge by Jenkinson on the touchline.
The man to replace him was Andrews, but before he could get on Santos fired a long-range effort just past the right-hand post.
At the other end Long flicked on a long ball for Fortune, who held off Jenkinson and spun him in the box - but he could not generate enough power in his shot to beat Szczesny.
The assistant referee awarded a dubious corner on 55 when the ball did not appear to have touched McAuley, with van Persie challenging him.
From van Persie's flag-kick Fulop's nightmare continued as he punched the ball back towards his own goal and allowed Koscielny to volley into the empty net.
Albion refused to hang their heads and just past the hour-mark van Persie was forced to clear Olsson's header from Dorrans' corner off the goalline.
Andrews spun on Mulumbu's pass in the 71st minute and rifled in a 20-yard shot that Szczesny dived to his left to beat out.
Substitute Peter Odemwingie found Fortune out wide on the right on 81 and he cut inside - but screwed his 18-yard shot well wide of the left-hand post.
Three minutes from time Long teed up Fortune, who saw his goalbound strike from a central position blocked by Koscielny.
Song presented flying Dutchman van Persie with a chance to beat Thierry Henry's 30-goal season for the Gunners in stoppage time - but he blazed over.
And there was still time for Jones to burst into the box, only to be thwarted by substitute Kieran Gibbs as he slid in to block just as the Baggies right-back pulled the trigger in a bid to equalise.
ALBION (4-4-2): Fulop, Jones, McAuley, Olsson, Ridgewell; Cox (Odemwingie 74), Morrison (Andrews 52), Mulumbu, Dorrans (Scharner 79); Long, Fortune. Subs not used: Daniels (gk), Hurst, Shorey, Dawson.
ARSENAL (4-4-2): Szcesny; Jenkinson, Koscielny, Vermaelen, Santos (Ramsey 79); Rosicky (Walcott HT), Coquelin, Song, Benayoun; Gervinho (Gibbs 67), van Persie. Subs not used: Fabianski (gk), Chamberlain, Djourou, Chamakh.
GOALS: ALBION - Long (12), Dorrans (15). ARSENAL - Benayoun (4), Santos (30), Koscielny (55).
BOOKINGS: ARSENAL - van Persie (foul 38).
REFEREE: M Jones (Chester).
ALBION STARMAN: Shane Long.