Albion never recovered after conceding three goals in the opening 24 minutes to slip to only their second WSL defeat of the season.
Beth Mead, Caitlin Foord and Frida Maanum scored to put Arsenal in control at the Emirates. Albion improved after the break and Kiko Seike hit the bar but the damage had been done and the Gunners got a fourth through substitute Lina Hurtig with 15 minutes to go before Alessia Russo made it 5-0 with an injury-time penalty.
Dario Vidosic made three changes to the team which had beaten Leicester City last time out with Maria Thorisdottir, Seike and Maisie Symonds all recalled.
Albion started confidently enough and enjoyed good spells of possession but they fell behind after 13 minutes. The defence failed to cut out Maanum’s diagonal ball to Mead on the right. She cut inside Poppy Pattinson and bent a left-foot shot in off the far post.
Arsenal had lots of joy down their right-hand side in the first half and profited again in the 22nd minute. Neither Seiko nor Pattinson spotted Kim Little’s run into the box when she was found by Emily Fox. Little fired the ball across the face of goal and Foord made no mistake from two yards.
Maria Thorisdottir challenges Caitlin Foord. 📷 by Kyle Hemsley.
It was to get worse two minutes later when Arsenal made it 3-0 but on this occasion there was little Albion could do when Maanum curled a shot from the left-hand edge of the box into the top corner. On all three goals keeper Sophie Baggaley had no chance.
It nearly went from bad to worse when Foord’s shot from 25 yards came back off the post and Guro Bergsvand was booked for bringing down Fox when Arsenal threatened again on transition. Baggaley then made a terrific save in stoppage time when she pushed out Katie McCabe’s free-kick from the left-hand corner of the box.
Albion were forced into a change early in the second half when Thorisdottir went down with an injury.
The visitors went close to pulling one back when Manuela Zinsberger made her first save after 65 minutes, pushing Seike’s shot round the post.
Poppy Pattinson challenges Beth Mead. 📷 by Kyle Hemsley.
The Japanese winger went even closer two minutes later. Symonds’ pass found her in space, and she turned to beat Zinsberger with a right-foot shot which clipped the crossbar as Albion enjoyed their best spell of the game.
A combination of Baggaley and Rachel McLauchlan somehow prevented Foord from bundling the ball over the line from two yards out, but the hosts did get a fourth when Hurtig’s glancing header from McCabe’s inswinging corner went in despite Symonds’ efforts to hook it off the line.
And a miserable night was completed in stoppage time when Russo made it 5-0 from the penalty spot after Jorelyn Carabali fouled Stina Blackstenius in the box and substitute Aisha Masaka had to be stretchered off with a shoulder injury.
Albion: Baggaley, Thorisdottir (sub: McLauchlan 48), Bergsvand, Carabali, Seiko (Masaka 86), Losada (Olislagers 86), Symonds, Pattinson, Kirby (Vilamala 86), Parris.
Subs not used: Poulter, Loeck, Rayner.
Referee: Amy Fearn
Attendance: 22,467