Clive Dickens, chief operating officer at Virgin Radio, said that he and O'Connell had agreed that there was an "element missing" from his show and that he needed someone to chat with.
Dickens said: "Christian was a ringmaster doing all the acts himself. Vicky will not be a co-host -- she will be a team member. But she will be there to help.
"Christian used to have sidekicks at other broadcasters and we wanted to give some of that back."
Butler-Henderson will join the show in the next few weeks as part of a team including Ritchie Firth who recently joined the breakfast show as executive producer and Brian Murphy, producer on the show.
Firth replaced Roque Segade Vieto who moved to the newly created role of executive producer across the whole station.
Butler-Henderson said: "This is a fantastic opportunity -- the chance to work with Christian and his team on what is an amazing breakfast show, and working with people who have the vision and the means to re-write the definition of radio is too good an opportunity to pass up."
Butler-Henderson also appears in Tiff Needell's Sudden Impact DVD out on October 6.