Intrapartum nurses assume a central role in the birth process and make decisions driven by a set of beliefs. Therefore, the purpose of this study was to develop a valid and reliable instrument to measure birth beliefs of intrapartum nurses related to birth practice. A total of 313 intrapartum nurses accessed this online, self-administered instrument over a 3-month period. The Theory of Planned Behavior guided development of the Intrapartum Nurses' Beliefs Related to Birth Practice scale and provided a basis for the connection between beliefs and practice. This article describes the psychometric analysis of the instrument. Findings include a moderate, positive correlation with a similar instrument, a Cronbach α of 0.797, and 2 factors identifying belief systems. With further revision, this instrument may provide an accurate measure of the birth beliefs of intrapartum nurses.