Chilton, 34, joins BTC after spending two seasons with Motorbase Performance in 2018-19, winning two races and finishing third in the championship in his first season with the team. The former WTCC racer placed 10th overall last year.
He joins the previously-announced Josh Cook for the 2020 campaign.
"The team did a sterling job last year," said Chilton, who has previously represented Honda in the BTCC as part of the Arena Motorsport and Team Dynamics squads.
"To have ended the season fourth overall and as independent runners-up in their first season running the FK8 chassis was an outstanding achievement. I can't wait to get testing underway.
"I have a great history with Honda, and I'm really looking forward to getting back into one again, and behind the wheel of the FK8 [Civic]. Josh [Cook] is a great driver, and I like having good teammates to push me.
"I'd like to think that with my years of experience I can bring something new to the team and help to push them on at the sharp end of the grid.
"BTC Racing is a relatively young team, but their attitude and performance caught my eye last year. I like their approach and professionalism.
"I'm optimistic about the future that we can build together, not just for this season, but hopefully for many years moving forward."
Joint team Principal Bert Taylor, who owns the operation alongside racer and businessman Steve Dudman, said: "Personally I couldn't be happier to have captured Tom. You only have to look back over his racing career to see what a true talent he is.
"Tom's signing is another part of our plan to push forward and challenge for the BTCC title in 2020. He brings a wealth of experience and talent to the team, and I have no doubt that his knowledge will help to develop the Civic further this season."
Josh Cook, BTC Racing Honda Civic
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