Terms of the deal were not disclosed.
The acquisition of the Chicago-based Ellwood adds 105 retirement plans with about $55 billion in assets under advisement to CAPTRUST's client roster, a CAPTRUST spokeswoman said.
In addition to retirement plans, Ellwood serves endowments and foundations, hospitals, family offices and high-net-worth individuals.
The firm has 200 clients overall, representing $85 billion in total assets, which will be added to CAPTRUST's roster, according to the release.
The acquisition also will give CAPTRUST its first location in Chicago and bolster its presence in Denver, the news release said.
As part of the deal, which is expected to close in the fourth quarter, a total of 55 Ellwood employees will join CAPTRUST.
The transaction follows CAPTRUST's acquisition of six other RIA firms this year, such as Nachman Norwood & Parrott Wealth Management and Cammack Retirement Group.
CAPTRUST has been on a buying spree since 2006, acquiring 51 firms to date. As of June 1, the firm had more than $60 billion in assets under management and more than $600 billion in assets under advisement.