A mobile mashup should be able to compose the component services in accordance with a user's context. We propose a context-aware mashup method for smart mobile devices. For this purpose, a novel user request model is presented and the conventional service description model is extended. We propose a context ontology which can efficiently manage contextual information in a mobile environment. Furthermore, the proposed method undergoes three computations - functional, I/O connectable and contextual matching. In particular, the contextual matching technique utilizes two types of contextual information that are proposed in this paper, implicit and explicit contexts. In order to evaluate the accuracy of the proposed method, a test registry based on real world Web APIs was built. Experimental results show an overall improvement of 26.7% in precision compared with the case where contextual information was not utilized.