Avenell is a former general manager of human resources for Westpac and general manager of people & culture for the New Zealand Post Group.
"The board and partners are well into implementing all of the recommendations following Dame Margaret Bazley's review of the firm released in July. We have charged ourselves with building a culture and a firm that reflects the values and aspirations of our people and clients," Crotty said.
"Jo is a strong and accomplished executive who is hugely respected, and who will inspire confidence, help overcome obstacles, and lead by example. Russell McVeagh will benefit from Jo's proven track-record delivering significant cultural change across large organisations."
Following allegations of sexual harassment towards five summer clerks over the summer of 2015/16, Bazley's 89-page report found that junior lawyers and other young staff were encouraged to "drink to excess" in that period, in a culture that had instances of crude, drunken, and sexually inappropriate behaviour.
Bazley noted failings in the firm's governance and policies, including no code of conduct, which she said contributed to poor management of the incidents.
Avenell's appointment is effective on 23 October, replacing outgoing CEO Gary McDiarmid.