Purpose: This study was conducted to develop nursing practice guideline for delirium of cancer patients and to evaluate the effects of the guideline. Methods: Guideline development was done by guideline adaptation and de novo development of recommendations. Participants consists of 13 nurses and 90 cancer patients (intervention group: 36, control group: 44) in oncology unit. One group pre-post test design for nurses and nonequivalent control group non-synchronized design for patients were used. Data were analyzed by χ2-test, t-test, paired t-test and ANCOVA. Results: Guideline consisted of 3 domains and 106 recommendations. The number of recommendations in each domain were: nursing assessment, 23; nursing intervention, 80; nursing evaluation, 3. There were 5.6% of A, 17.0% of B, 20.8% of C, 56.6% of D in grade of recommendations. There were significant differences in nurse’s knowledge about delirium, nursing performance and care stress of cancer patients with delirium between before and after guideline implementation. There were no significant differences in the incidence of delirium, episodes of delirium, delirium severity, and duration of hospital stay in cancer patients between experimental and control group. Conclusion: Study findings indicate the implementation of evidence-based nursing practice guideline for cancer patients with delirium can be recommended in nursing practice.