Objective: The aim of this study was to investigate whether omitting elective inguinal irradiation during neoadjuvant or adjuvant (chemo)radiotherapy is feasible for patients with locally advanced low rectal cancer (LALRC) with anal canal invasion (ACI). Study design: A total of 90 LALRC patients with ACI who underwent neoadjuvant or adjuvant (chemo)radiotherapy between 2011 and 2021 were recruited. Inguinal lymph node (ILN) was clinically negative on presentation. Failure pattern, ILN recurrence rate, survival data and prognostic factors were analysed. Results: The 3-year ILN failure rate was 4.94%. 1 patient developed isolated ILN failure, which was successfully salvaged by surgery. The 3-year locoregional disease free survival (LRFS), distant metastatic recurrence free survival (DMRFS), and overall survival (OS) were 81.1%, 77.0%, and 86.8% respectively. In multivariate cox regression analysis, positive pathological lymph node after neoadjuvant treatment predicted worse LRFS (odd ratio [OR] 10.57, P= 0.00001), DMRFS (OR 9.17, P= 0.0002), and OS (OR 12.92, P= 0.0005). Positive tumour resection margin correlated with worse LRFS (OR 23.53, P= 0.001), DMRFS (OR 12.62, P= 0.002) and OS (OR 47.24, P= 0.002). Concurrent chemotherapy to RT was associated with better LRFS (OR 28.32, P= 0.002). ≥ Grade 3 acute and chronic toxicities occurred in 44.4% and 11.1% respectively in patients with elective inguinal radiation compared with 19.8% and 11.1% respectively in patients who did not receive it. Conclusion: Omission of elective inguinal irradiation was associated with a low inguinal failure rate for LALRC with ACI. It can spare patients from unnecessary acute radiotherapy toxicities.