The interpreter's role generally assumes three dimensions: the interpreter's own attitudes towards his/her role, the institutional requirements specified in the codes of conduct for professional interpreting, and the expectations and attitudes that interpreting service users have of the interpreter. With the role descriptions of the three parties compared and contrasted, this paper attempts to draw a real picture of the interpreter's role through empirical studies from a sociolinguistic perspective. It is observed from real life interpreting events that an interpreter usually acts simultaneously as a translator (an animator with no turn management), a discourse process coordinator (an animator or author with some turn management), and a discourse co-constructor (an author with substantial turn management), exerting certain influence on the direction and/or outcomes of the interaction in an explicit or implicit way. Such a role performance often deviates from the role descriptions of the institutional norms and interpreting service users. It is the paper's conclusion that given the complexity of both the macro and micro context of an interpreter-mediated encounter and of the relationships between the interpreter and each client, the interpreter's role can be ambiguous, complicated and multidimensional and defies any simplified and decontextualized definitions.