Sydney Rae Leroux was born in Surrey, British Columbia, Canada on May 7, 1990. Her father was an American baseball player named Ray Chadwick, who had pitched seven games for the California Angels in 1986. Her mother, a Canadian by the name of Sandi Leroux, was also a baseball player, having played as third baseman for Canada's softball team at the 1987 Pan American Games. However, her parents split up three months into the pregnancy. Sydney's mother raised her primarily, sending her to Johnston Heights Secondary School in Surrey where she mainly focused on soccer, but also track and field.
After winning numerous soccer championships throughout high school, Sydney eventually became the youngest player to ever join the Vancouver Whitecaps squad at the age of 15. She then went on to win a championship with Team BC at the Canada Games in 2005. However, from a young age, Sydney had always wanted for the United States national soccer team, so afterwards, she moved to Scotsdale, Arizona In order to pursue that dream. She would then attend UCLA, where she joined the Bruins soccer team.
Upon graduating, Sydney was the number one pick by the Atlanta Beat in the 2012 WPS (Women's Professional Soccer) Draft. Unfortunately, the league went belly up before she even had a chance to play, so she decided to join the Seattle Sounders Women in the W-League instead. The very same year, she was also a member of the U.S. Olympic Women's Soccer Team, which went on to win the gold medal in a 2-0 victory over New Zealand. She was even responsible for scoring one of the goals in a quarter finals match against New Zealand. Since then, Sydney went on to sign with the Boston Breakers for the inaugural year of the National Women's Soccer League, and has continued to play with them since.