Aegis acquired Comcon through Synovate, its market research group, for an undisclosed amount. According to the terms of the deal, it could acquire the remainder of the business in 2015.
Comcon, which has offices in Moscow and St Petersburg, produced $18.9m (£12.1m) of sales in 2009 and has 200 employees.
Aegis chief executive Jerry Buhlmann said the acquisition would give it the scale to expand further in the relatively immature Russian market research sector.
Meanwhile, Aegis Media has appointed Simon Francis as its new chief executive for the Europe, Middle East & Africa (EMEA) region.
Francis, who was poached from rival Saatchi & Saatchi, will report directly to Buhlmann.
Buhlmann said: “Simon has a wealth of experience both in the sector and the region with an impressive track record which speaks for itself.”
Francis said he was “delighted” to be joining Aegis, which he said had “an amazing track record of innovation.”