The 30-year-old, who missed the Lionesses' victorious European Championship campaign last summer with a knee ligament injury, has signed an 18-month deal with an option to extend.
Nobbs won three WSL titles and four Women's FA Cups during a 12-year spell with the Gunners, and returned to the national team set-up for last September's World Cup qualifiers against Austria and Luxembourg.
She has featured in all nine of Arsenal's WSL fixtures this season, including during their 4-1 win at Villa Park in December, as they look to win back the title they last claimed in 2019.
“This is a big signing for us and Jordan is one of the country's most decorated footballers,” Villa manager Carla Ward told the club's website.
“She's a winner and will bring a wealth of experience that her new team-mates will thrive off.
“We're delighted to secure her signature and we hope this move can help the football club as well as cement her place back in the international set-up.”
Additional reporting by PA.