Spiritual care and chaplaincy have been part of the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Distress Management since the first meeting of the panel in 1997, possibly the first time this degree of spiritual care and chaplaincy care integration occurred in cancer care. Since that time, the chaplaincy care section of the guidelines, especially chaplain assessment categories derived from a spiritual care assessment, have provided a major resource for healthcare chaplaincy and have served as a model for integrating chaplaincy into the overall team practice of healthcare. However, this section of the NCCN Guidelines has not been substantially updated since it was originally written. During those 20 years, the practice of healthcare chaplaincy and the research that supports it have grown substantially. In the last year, at the request of the panel, we have updated the chaplaincy care section to fully integrate recently published evidence in spiritual care in healthcare, adding more value to this important set of guidelines. Those updates appear in the 2019 version of the NCCN Guidelines. This article discusses the history of chaplaincy involvement in the NCCN Guidelines for Distress Management and the precedent it set for the integration of chaplaincy in other efforts that followed. Integration of this section of the Guidelines into the spiritual care practice at Memorial Sloan Kettering Cancer Center is presented as an example of how these guidelines can be put into practice to improve patient care. Finally, a summary of the recent research by Drs. Kenneth Pargament and Julie Exline is presented as the foundation for the revised chaplain assessment categories and interventions.