© 2014 IEEE. In a highly competitive global service market, service consumers tend to select a provider from a large pool of functionally equivalent services based on Quality of Service (QoS). To gain competitive advantages, it is desirable for a service provider to adopt service customization, particularly QoS customization, as one of the key strategies to differentiate itself from the competitors. This, however, has raised new challenges in describing and publishing QoS information, identifying users, and adjusting QoS offerings. This research borrows the concept of attribute based access control and presents an attribute based service customization model. The attribute based access control policy language is extended to enable definition of QoS customization rules. An algorithm is proposed to support consumer identification and QoS customization. This paper also discusses a case study to illustrate the proposed approach.