Andrew J. McKenna, chairman of IMS and CEO of Schwarz, was unavailable for comment but in a prepared statement lauded "the power of the Omnicom network and resources."
Schwarz is a major supplier of paper and production to McDonald's Corp.
Second acquisition this week
Last week AdAge.com reported that Omnicom was backing startup security consulting firm SafirRossetti.
An Omnicom spokeswoman confirmed the deal but declined further comment.
Several executives close to Omnicom said the holding company was on a buying spree of hot marketing and communications services concerns as clients divert advertising spending into other disciplines.