Traust Sollis, which has offices in New York and Princeton, N.J., was founded as a certified public accounting firm in 1982 by Al Zdenek Jr.
Mr. Zdenek will join Mercer, along with Richard Weyers, the firm's chief operating officer and chief compliance officer, Brian Picariello, its head of wealth management, and 26 staff members. Terms of the acquisition were not disclosed.
The firm's services include tax-planning strategies for high-net-worth individuals and families.
In a release, Mercer said the acquisition brings its assets under management to more than $12 billion and its national offices to 29.