The off-spinner has been included in Surrey's 13-man squad for the fixture.
Ashwin will turn up for Surrey in their County Championship fixture against Somerset at the Oval from Sunday (July 11).
Ashwin, who has played for Nottinghamshire and Worcestershire in the past, will join Hashim Amla as the second overseas player for Surrey in their final Group 2 match.
The off-spinner has been included in Surrey's 13-man squad for the fixture.
"I am so privileged to be having the badge on. I have heard and wondered what the London counties are all about. Even though it's only for a game, I am delighted to share this dressing room," Ashwin said in a video shared by Surrey.
Just like the rest of the Indian squad, Ashwin was enjoying a break from the bio-bubble life following the ICC World Test Championship final against New Zealand last month.
By playing this match for Surrey, he will get valuable match practice before the five-Test series against England, slated to start on August 4 at Trent Bridge.
The Indian squad will reportedly assemble in London on July 14, before travelling to Nottingham to start their preparations for the England Test series.