The 22-year-old has signed a fully professional three-year contract with the French side and begins training on Monday.
“Although I was only half way through my contract with Arsenal, we parted on good terms,” Beattie said. “One of the problems was that I couldn’t establish myself in one position.”
Played mainly as a full back at Arsenal, Beattie replaced Julie Fleeting as the main striker in the Scotland side before long-term injuries to Ifeoma Dieke and Rachel Corsie saw her moved back to centre half at the start of this year.
“I’ve enjoyed playing different positions, and it has no doubt helped my game, but I’ve pinned it down with Montpellier that I will play at centre-half,” the 68-cap player pointed out.
“I can now work hard on that position with my club as well as Scotland. [Scotland coach] Anna Signeul was positive about the move and thinks it will be a good one for me.”
Although she will have to brush up on her French, Beattie will have little difficulty settling into her new environment. Her brother Johnnie plays rugby for Montpellier and revitalised his Scotland career after moving to France last year.
He got married to partner Jen in St Andrews earlier this month, and Beattie, who has scored 17 goals for Scotland, said: “I’ll stay with them at the start.
“Of course, it was a consideration that they live there already – I’ve hardly seen him in the last year and now I’ll get a chance to watch some of his games as well.”
Montpellier finished fourth last season in a women’s first division dominated by former Champions League winners Lyon and Paris Saint-Germain.
“Only the top two get to play in the Champions League, so I will miss that after playing in semi-finals for Arsenal,” Beattie said.
“But Montpellier have signed a few players over the summer and getting into the Champions League is their main aim.”
Beattie follows trail-blazer Rose Reilly in playing professional football in France; the 58-year old, who is in the SFA Hall of Fame, signed for Reims in 1974 before joining AC Milan.