The Matildas star, who scored the match-winning goal in Australia's Round of 16 win over Brazil and a brace in the group win over Nigeria, agreed to a one-year deal with the National Women's Soccer League outfit, pending an international clearance.
It will be the 24 year-old's second stint in Boston, having played there during the 2012 Women's Premier Soccer League Elite season and then the 2013 NWSL campaign.
In those two years with the Breakers, Simon made 30 appearances and scored 15 goals with five assists.
"I am delighted to be bringing Kyah back to Boston. She had a fantastic stint with us in 2012 and 2013, and if not for her injury, she would have continued as a Breaker," Breakers general manager Lee Billiard said.
"She has shown her sharpness and eye for goal during the World Cup, something we will benefit from in Boston upon her return from international duty. I am happy to have her back scoring goals in a Breakers jersey."
