The field of English for Specific Purposes (ESP) is based upon collaboration between ESP practitioners and subject experts. The degree of collaboration between these groups of teachers varies a great deal in the field overall. The highest level of collaboration is the team teaching of self-contained courses. Collaboration of any kind is fraught with challenges. Co-teaching university courses in interdisciplinary teams presents ESP practitioners with special problems, as well as rewards. This article is a case study of an institution-wide experiment in ESP team teaching continuing at a small four-year English-medium liberal arts college located in western Japan. This is an exploration of the interaction between interdisciplinary teaching partners at the beginning stages of collaboration. Specifically, this article examines how team teaching with discipline specialists can affect the status of ESP professionals, as well as influence pedagogical practices. This case study of interdisciplinary team teaching aims to offer general guidelines for any level of collaboration between ESP and subject specialists to succeed.