Abstract Background It was hypothesized that preparing for a surgical procedure, taking into account individual patient characteristics, may facilitate the procedure and improve surgical quality. The aim of this study was to compare different case-specific, preoperative mental rehearsal methods before minimally invasive rectal cancer surgery. Methods In this RCT, patients were allocated in a 1 : 1 : 1 : 1 ratio to four groups: systematic mental rehearsal (SMR) using MRI scans; SMR and three-dimensional (3D) virtual models; SMR and synthetic 3D printed models; and routine practice (control group). Surgeons operating on all but the control group underwent mental rehearsal with the visual aids, including axial MRI scans of the pelvis, interactive 3D virtual models reconstructed from axial MRIs, and synthetic models, manufactured by 3D printing. Operations were video-recorded and assessed by two experts blinded to allocation using two validated scores, the Competency Assessment Tool (CAT) and Objective Clinical Human Reliability Analysis (OCHRA). The primary outcome of the study was surgical performance, measured by the CAT. Results Forty-nine patients were randomized and allocated to the four groups. There were 12 participants in each of the control, MRI and SMR, and virtual and SMR groups, whereas the SMR using physical models and simulation group included 13. No difference was observed between groups in median CAT scores (control 30.50, MRI 34.25, virtual 31.75, physical 34.00; P = 0.748, partial η2 <0.001, where pη2 is indicative of effect size) or OCHRA scores (anterior, posterior, right and left lateral planes, transection P>0.200, pη2 =0.052–0.088). Time spent not performing dissection was significantly shorter for the SMR with MRI group than for the control (57.5 versus 42 respectively; P < 0.001, pη2 =0.212). Conclusion Mental rehearsal did not affect CAT and OCHRA scores of consultant surgeons. Reference number: ISRCTN 75603704 (https://www.isrctn.com).