Marketing services businesses are those that provide outsourced promotional, advertising, production and other marketing-related services to firms that lack the appropriate internal resources to do so or those looking for specialized expertise outside the realm of their core business.

Marketing services providers include both interactive and direct marketing agencies, as well as others that support direct marketing and customer relationship management, such as search engine, e-mail and affiliate marketing firms; mail production, fulfillment, call center and list brokerage companies; as well as providers of loyalty and lead generation services, among others.