The CIA founder is buying The Brand Company, which will become a hub office alongside Ingram's London and New York operations.
The Brand Company is being rechristened The Ingram Brand Company and its partners, Peter Wilken and James Stuart, will become its managing partners, responsible for the Greater China region.
The intention is to have two more offices in China in the next two years.
Ingram, who set up his consultancy in September 2003, said: "With three offices in three continents, you could say our momentum has been pretty good. Hong Kong is very much a stepping stone into Greater China."
The Brand Company, which was set up three years ago, has a client list including SmarTone-Vodafone, Shangri-La Hotels and the Hong Kong Trade Development Council.
Stuart has extensive client-side experience while Wilken is a former managing director of BBDO Asia-Pacific. Part of their deal, which comes after almost a year of negotiations, will be in the form of an earn-out over the next three years.
Ingram said: "James and Peter have a range of experience and between us we have complementary skills."
Ingram acquired the New York marketing consultancy Consumer Dynamics seven months ago. It will be rebranded Ingram by the end of the year.