The Gunners wrapped up their first signing of the summer tonight by announcing that they had acquired the 25-year-old from Barcelona for a fee in the region of £30m.
Walcott, who may yet find himself competing with Sanchez for a starting berth next term, took to Twitter to convey his delight over the news.
He wrote: "What a Signing!!!!! Can not wait and looking forward to playing with Alexis Sanchez!!!!! #COYG."
Sanchez could be followed to North London by Newcastle United defender Mathieu Debuchy, who is expected to swap St James' Park for the Emirates in the near future.