Parker was previously halls director for Earls Court. She has worked for EC&O Venues since 1994.
Her expanded role includes responsibility for the Olympia customer services department, which was previously carried out by Debbie Law, who leaves the company at the end of January to pursue other opportunities.
Parker said: "I'm excited about working with my colleagues at Olympia more closely and uniting the two customer service departments. By working together, I hope the venues' successes will continue long into the future."
EC&O Venues group managing director Nigel Nathan said: "Since 2001, Rachel has led the Earls Court customer services team with passion and dedication, and I've no doubt that she will continue to demonstrate such professionalism across both venues."