Inaccurate body temperature measurements impact clinical decision-making and patient safety. Nurses in our large free-standing children’s hospital and clinics questioned the accuracy of certain thermometer devices. Our clinical practice policy on temperatures allowed nurses to use their clinical judgment about which device and route of thermometry should be used for their patients. An audit of our hospital and clinic thermometer purchases from January to May 2014 revealed seven different devices. The purpose of this evidence-based practice (EBP) project was to select the most precise and accurate temperature-taking routes and measurement methods to set as the standard for our hospital system. The evidencebased project began with the intent to conduct a systematic review of the literature on the accuracy of non-core thermometer devices. While developing evidence tables, it became clear that the results and conclusions of the studies were so inconsistent that we could not select the most accurate thermometer devices for our hospital system. We realized only studies comparing core vs. non-core were appropriate, and a meta-analysis was required to summarize data from core vs. non-core temperatures. Evidence shows that oral and rectal electronic thermometers provided the most accurate approximation of core body temperatures. Our findings resulted in a revision of the temperature policy. One year after the policy change, unit-by-unit observations of devices showed significant usage of approved devices. This successful practice and policy change improved clinical decisionmaking based on more accurate and consistent body temperatures.