In an email to staff, executive vice-president Heather Conway said Janice Rubin would begin her work immediately.
Conway urged anyone who worked on "Q" or an earlier Ghomeshi show — "Play" — to contact Rubin with any complaints, concerns or experiences involving harassment, discrimination, violence or other inappropriate workplace conduct.
"If you have any information you wish to share, I strongly encourage you to come forward in order to ensure the investigation is as thorough as it must be," Conway said.
"Please be assured, these conversations will be handled sensitively and any individual who comes forward will be treated with care and respect."
While maintaining confidentiality, Rubin will report to senior CBC management about what she heard and what her investigations uncovered along with recommendations on resolving any complaints.
The investigator will also report separately on what the broadcaster should do to prevent any similar issues arising in the future.
Rubin is described on the law firm's website as an award-winning workplace investigator who has made guest appearances on CBC as an expert. She refused to comment on whether this posed a conflict of interest.
"As a leading authority on workplace harassment, Janice has often offered her views on this subject to a number of media outlets and we see no conflict of interest," said CBC spokesman Chuck Thompson.
The CBC fired Ghomeshi, 47, on Oct. 26 after seeing what it called "graphic evidence" that he had caused physical injury to a woman.
He is also under criminal investigation after at least three women complained to Toronto police he had physically or sexually assaulted them.
Earlier Tuesday, a spokesman for the broadcaster confirmed the most senior producer at "Q," Arif Noorani, was taking time off.
"He decided to take some time while we get more clarity around this situation," said Thompson, head of public affairs for English services.
Noorani is reported to have been told by a union representative of allegations made by a former producer that Ghomeshi had grabbed her and made a lewd suggestion.
In an email made public by the CBC on Tuesday, Noorani said, "At no point was an allegation of sexual harassment brought to my attention."
One source has also told The Canadian Press that the young woman, who has chosen not to be identified publicly, made no allegations of serious harassment to the union volunteer or Noorani despite her insistence that she did.
"They both said she didn't tell them that — the sex details," the source said.
"She just said he yelled at her — they were going over a script — and stormed out."
In all, nine women — most anonymously — have spoken to media outlets about how Ghomeshi, without warning, attacked them.
Of the three who have complained to police, only actress Lucy DeCoutere, star of "Trailer Park Boys," has agreed to be identified.
Toronto Police Chief Bill Blair rejected any notion that women who believe they have been assaulted by Ghomeshi should somehow be compelled to make formal complaints or talk to investigators.
"I've been somewhat surprised by the number of men who have written to us or come forward to suggest that we should force people to come forward and to participate in the criminal justice system," Blair said. "That attitude is shocking to me in the 21st century."
Ghomeshi, who faces no charges, admitted in a lengthy Facebook posting to having a proclivity for rough sex but insisted his encounters with women were consensual.
He has said he would meet the flurry of allegations "directly" but has yet to do so.
In a statement, Carmel Smyth, the president of the Canadian Media Guild which represents unionized employees at the CBC, said she was "saddened and disturbed" by the reports and revelations around Ghomeshi.
Smyth acknowledged changes may be required to deal with the "structural issues and silences" that can enable harassment and abuse.
"The best chance we have of really addressing abuses is to work together to change the cultures and conditions that allow them to take place," Smyth said in a statement.
"That means holding ourselves accountable, and holding our employers and the wider community accountable as well."
Ghomeshi has filed a $55-million lawsuit alleging defamation and breach of confidence against the CBC. He has also filed a union grievance alleging wrongful dismissal and defamation.