The deal will see Lemon Sky, which employs around 70 people, based in Warsaw and Wroclaw, become wholly owned by JWT.
Lemon Sky, which works with Orange, Tesco, Leroy Merlin and Nestlé, reported unaudited revenue last December of €2.7m.
WPP generates around $150m in Poland each year, employing over 1,000 people.
Source: The Drum