Nontechnical skills, such as teamwork and communication, are critical to safe care delivery, but can be difficult to measure. This systematic review examined validated approaches for assessing nontechnical skills using direct observation. Researchers analyzed 118 articles that discussed 76 unique tools for measuring nontechnical skills. This wide range of instruments assessed individuals or teams in various health care settings, either in simulation or actual clinical practice. They identified substantial variability in how these approaches were validated and whether individual studies reported the usability of each tool. The authors spotlight the need for standardization in how to develop, test, and implement assessments of nontechnical skills. A related editorial discusses the findings of this systematic review in the context of previous research and advocates for future work to standardize assessment of nontechnical skills in health care.