Longtuo has e-commerce expertise in creative, customer acquisition and marketing solutions.
The company, set up in 2000, employs 140 people in its Beijing, Shanghai and Guangzhou offices.
Publicis said that Longtuo will form part of its Razorfish business in China, which currently employs 130 people and provides e-commerce services to clients including Converse and Hertz.
Longtuo's existing clients include Renault as well as a number of blue-chip Chinese firms.
As part of the acquisition, Longtuo's chief executive and founding partner, Su Yi, will become managing director of the new entity, called Longtuo China.
Su Yi will report to Vincent Digonnet, president of Razorfish Asia Pacific and executive chairman of Razorfish Greater China.
In 2009, Publicis acquired digital ad agency Razorfish from Microsoft for around $530m, as the French advertising giant sought to bolster its digital revenues.