The aim of this study was to identify whether certain cognitive factors, such as irrational beliefs and anger rumination, affect nurses’ anger expression styles. A total of 335 nurses employed at four tertiary hospitals in Korea completed surveys between July 29 and September 25, 2015. The surveys included Shortened General Attitude and Belief Scale, the Korean Version of the Anger Rumination Scale, and the State-Trait Anger Expression Inventory–Korean version. Results revealed that higher levels of irrational beliefs and anger rumination were associated with more anger-in and anger-out, and less anger-control expressions. Findings indicate that the presence of specific cognitive characteristics could lead to maladaptive anger expressions. Active consideration of these cognitive risk factors is essential when developing anger-management programs for nurses.