Pain after surgery remains a major health problem, calling for optimized treatment regimens to maximize the efficacy of pharmacological interventions. In this randomized controlled trial, we tested in a routine surgical treatment setting whether postoperative pain can be reduced by a brief preoperative intervention, i.e., positive verbal suggestions in combination with sham acupuncture, designed to optimize treatment expectations. We hypothesized that the expectancy intervention as add-on to patient-controlled intravenous analgesia (PCIA) with morphine reduces patient-reported postoperative pain and improves satisfaction with analgesia.Ninety-six women undergoing breast cancer surgery were randomized at two stages: Prior to surgery, anesthesiologists delivered either positive or neutral verbal suggestions regarding the benefits of acupuncture needling on postoperative pain ("information condition"). Patients were then randomized to receive sham acupuncture or no sham-acupuncture during postoperative care ("sham acupuncture condition"). Average pain during the 24h observation period after surgery as primary and satisfaction with analgesia as secondary outcome were assessed with standardized measures, and analyzed with ANCOVA accounting for morphine dose, surgery-related and psychological parameters.Postoperative pain ratings were significantly reduced in patients who received positive treatment-related suggestions (F=4.45, p=0.038, main effect of information). Moreover, patients who received an intervention aimed at optimized treatment expectations reported significantly greater satisfaction with analgesia (F=4.89, p=0.030, interaction effect).Together, our proof-of-concept data support that optimizing treatment expectations via verbal suggestions may offer a promising approach to improve patient-reported outcomes. Future translational and clinical studies are needed to test such psychological strategies in different surgical interventions, patient groups, and pharmacological treatment regimens.