After a cagey opening to the game, the Gunners fell behind on the half-hour mark as Ander Herrera ghosted in to volley in at the far post.
It was a blow for Arsène Wenger’s side but they refused to panic, sticking to their gameplan and upping the tempo after the interval.
Alexis Sanchez soon crashed a shot over the bar, before Olivier Giroud tested David de Gea and Marcos Rojo slid in to deny Aaron Ramsey in the box.
After a sluggish first-half showing, this was much more like it from Arsenal and Ramsey again went close when he lifted the ball over De Gea and forced Rojo into a last-ditch clearance.
Finally the pressure told as Walcott controlled the ball in the area and drilled a deflected shot past Manchester United substitute goalkeeper Victor Valdes.
It was no more than they deserved and they could have even gone on to win it as Giroud twice went close in the closing stages.
In the end the Gunners had to settle for a point, but the result means they can be confident of sealing third place and automatic entry to next season’s Champions League.
*Culled from www.arsenal.com