Purpose: The use of defunctioning loop ileostomy (DLI) in rectal cancer surgery, particularly during total mesorectal excision (TME) with primary anastomosis, remains debated. This study aimed to evaluate DLI utilisation, associated factors, and outcomes in rectal cancer patients managed with or without neoadjuvant chemoradiotherapy (nCRT). Methods: This retrospective cohort study analysed rectal cancer patients undergoing TME from 2004 to 2023. Patients were stratified into nCRT and straight-to-surgery (STS) groups. Outcomes included DLI formation rates, reversal rates, recurrence-free survival and complications. Data was analysed in SPSS ver.29. Results: Among 631 participants (64.3% male; mean age 62.1±11.4 years), DLI was formed in 60.9% (n=384). No significant associations were found between DLI formation and patient demographics and baseline characteristics. DLI formation was not significantly different between nCRT (63.0%) and STS (58.6%) groups (p=0.253). DLI rates were highest in ultralow anterior resection (ULAR) procedures (91.9%, p<0.001) and mid-rectal tumours (70.2%, p<0.001). DLI reversal rates were similar (nCRT:88.3%, STS:90.1%), with low reversal anastomotic leak rates (nCRT:4.1%; STS:3.7%). Stoma site incisional hernia rates were slightly higher in nCRT patients with DLI (14.1% vs 11.8%). Conclusion: DLI was utilised in 60.9% of cases, predominantly in higher-risk ULAR and mid-rectal tumours. There was no significant difference in the utilisation of DLI between the two groups, however, its utility is associated with considerable morbidity thus an individualised approach rather than one size fits all should be applied in clinical practice.