This multi-centre, two-armed parallel-group pragmatic randomised controlled trial (RCT) evaluated the effectiveness of a 3-day communication skills course in changing nurses' communication skills. The primary outcome was the change in the nurses' communication skills score from pre-course to 12 weeks post-course. The main secondary outcome was the change in the nurses' level of confidence in communicating with patients. A total of 172 nurses were randomised to the course or control. The communication skills score for the intervention group increased by 3.4 points post-course but decreased in the control by 0.05 points (between-group difference in change: 3.41, 95% CI: 2.16-4.66, P < 0.001). Confidence scores increased by 18.16 points for the intervention group but decreased 0.7 points in the control (between-group difference in change: 18.86, 95% CI: 13.39-24.34, P < 0.001). This RCT contributes to the evidence base on the effectiveness of communication skills training in cancer and palliative care.