Obesity (BMI > 30 kg/m2) is rapidly increasing worldwide with 26% of the UK population being obese and 38% being overweight. Obesity is intimately related to several life-limiting conditions including colorectal cancer (CRC). Obese patients have a higher degree of perioperative systemic inflammatory response (SIR) and an increased risk of perioperative complications. The aim of this current study was to investigate whether robotic-assisted surgery mitigates the effects of obesity in left sided CRC resections on the SIR and clinical outcomes. All patients undergoing left-sided colorectal cancer resections from May 2021 to May 2023 were, prospectively, entered into a database with patient characteristics and perioperative short-term outcomes recorded. CRP was considered a surrogate for SIR. The relationship between obesity and complications were examined using Chi Square for linear association, Kruskal–Wallis for continuous data and multivariate binary logistic regression model. 221 patients who underwent RAS for left-sided CRC were analysed. Obesity was associated with more comorbidity (ASA, p < 0.01) and SSI (p < 0.05) but not with age, sex, procedure or pathology. POD3 CRP < 150 mg/l was also associated with obesity (p < 0.01). In turn, greater comorbidity was associated with age (p < 0.001), site of resection (p < 0.05), SSI (p < 0.05), postoperative blood transfusion (p < 0.01) and LOS (p < 0.001). On multivariate analysis, only greater ASA (p < 0.05) and surgical procedure (p < 0.01) were associated with the development of an SSI independently. Greater comorbidity but not obesity was independently associated with postoperative SIR and clinical outcomes in patients undergoing RAS. These results support the use of RAS for left sided CRC resections, particularly in the obese.