Background <p>The Da Vinci single-port (SP) system has been shown to be safe and feasible for rectal cancer surgery; however, evidence on the learning curve remains limited. This study aimed to evaluate the learning curve for Da Vinci SP rectal cancer surgery using cumulative sum (CUSUM) analysis.</p> Methods <p>A single-center retrospective study was conducted on 73 patients who underwent SP robotic rectal cancer surgery, including 9 anterior resections, 51 low anterior resections, and 13 intersphincteric resections. The learning curve was analyzed using CUSUM for operative time and surgical failure, defined as conversion to open or multiport surgery, postoperative complications, or retrieval of fewer than 12 lymph nodes.</p> Results <p>The study cohort comprised 33 males and 40 females (mean age: 61 years). The mean operative time was 174.26 ± 44.91&#xa0;min (anterior resections: 145.33 ± 40.13&#xa0;min, lower anterior resections: 171.25 ± 33.86&#xa0;min, intersphincteric resections: 213.46 ± 55.55&#xa0;min). The mean number of harvested lymph nodes was 19.25 ± 6.58. CUSUM analysis identified two learning phases: Phase 1 (first 46 cases) had a mean operative time of 188.1 ± 35.7&#xa0;min, with a peak at case 46 in the CUSUM chart. Phase 2 (subsequent 27 cases) had a reduced mean operative time (155.4 ± 47.3&#xa0;min) with no reported complications. All complications occurred in Phase 1, including ileus (<i>n</i> = 2), urinary retention (<i>n</i> = 5), rectovaginal fistula requiring reoperation (<i>n</i> = 1), and anastomotic leakage treated with pigtail insertion (<i>n</i> = 1).</p> Conclusions <p>Surgical proficiency with the Da Vinci SP system was achieved after 46 cases, leading to improved efficiency and reduced complications.</p>