The objective of this study was to evaluate the effectiveness of a computer-assisted emergency preparedness course for school nurses. Participants from a convenience sample (52) of school nurses from New Mexico were randomly assigned to intervention or control groups in an experimental after-only posttest design. Intervention group participants completed 15 online emergency preparedness training modules followed by posttests, and control group participants completed the posttests without taking the training modules. Tests measured emergency preparedness with written exams, confidence surveys, and skills performance in videotaped scenarios; the videotaped scenarios were scored by Pediatric Emergency Medicine physicians blinded to whether the participants were in the intervention or control group. The intervention group participants scored significantly higher in tests of knowledge and skills than control group participants. Confidence Survey scores did not differ significantly. The online training modules are a valuable resource for improving school nurse emergency preparedness knowledge and skills but may not affect participants' confidence.