Background and Purpose: An education program to improve the delirium care competency of nurses is important as they play an integral role in caring for patients with delirium. This study aimed to examine the effects of a standardized patient (SP)-based delirium care education program on new graduate nurses' performance and self-confidence. Methods: A waitlist control group with a crossover design was adopted. The SP-based delirium care education program was designed, implemented, and evaluated. Generalized estimating equations were used to analyze differences in performance and self-confidence scores between the intervention and waitlist control groups. Results: The education program was found to significantly affect rater-assessed performance, SP-assessed performance, and self-confidence when controlled for gender and age. Implications for Practice: An SP-based delirium care education program improved new graduate nurses' performance and self-confidence in caring for patients with delirium. Nurse educators should provide experiential learning opportunities to ensure that recent nurse graduates have achieved optimal delirium care competency.