Sydney Fox was born on Betazed but before she was one years old her parents decided to move to Earth. They lived there until Sydney was 15 years old when they moved back to betazed.

Sydney studied at the Universty of Betazed, majoring in criminal psychology. Once she graduated Sydney spent a year working as a normal counselor until she was offered a job by an old Klingn friend. For about 5 years sydney worked on Qo'noS(Klingon homeworld) as a professional criminal psychologist and profiler.

It was only during the dominion war that Sydney joined Star-fleet and only after 2 months of joining she was transferred to Intelligence, she stayed in this area until the end of the war.

After the war Sydney decided no to go back to Qo'noS and stay with star-fleet, transferring back to the counselling department Sydney was posted on the USS Montgomery.