Teachers' use of inquiry has been studied largely without regard for the disciplines in which teachers practice. As a result, there is no theoretical understanding of the possible role of discipline in shaping teachers' conceptions and enactment of inquiry. In this mixed-methods study, conceptions and enactment of inquiry for 60 National Board Certified Science Teachers (NBCSTs) across the secondary science disciplines of biology, chemistry, earth science, and physics were investigated. A situated cognitive framework was used. Through the analysis of portfolio text (n = 48) and participant interviews (n = 12), themes emerged for participants' conceptions and enactment of inquiry. Findings suggested that disciplinary differences exist between NBCSTs' conceptions and enactment of inquiry. Furthermore, individuals teaching in more than one discipline often held different conceptions of inquiry depending on the discipline in which they were teaching. A key implication was the critical importance of considering the discipline in understanding science teachers' varied conceptions and enactment of inquiry. © 2011 Wiley Periodicals, Inc. Sci Ed96:48–77, 2012