Definition: An in-house advertising agency is owned and operated by its one and only client: the advertiser. Instead of a company outsourcing its advertising to an agency, its ad campaigns are mainly handled by its own in-house agency. Some advertising may still be directed to outside agencies, usually on a per-project basis.
Examples:
Teleflora's Super Bowl XLIII ad was created by its own in-house agency.
In 2002, Gateway pulled its $250 million advertising account from an outside agency to create its own in-house agency.