Kathy Vincent will take on the new role after the departure of Mr Thomas to AMP in January 2015.
Ms Vincent has led MLC's retail investment platforms team since joining the company in 2012.
In her new role, Ms Vincent will report directly to executive general manager for retail wealth products David Hackett.
Mr Hackett described Ms Vincent as a "strong leader" with a "deep understanding of the retail wealth industry".
"Her track record in this area is exceptional and we’re very excited to have her level of expertise in our business.
"MLC is committed to helping our customers build their wealth and save their retirement. Kathy will lead a team focused on this commitment at a time of great growth and opportunity for our customers," Mr Hackett said.
