<h4>Aims</h4>It is unclear whether inequalities in guidelines-recommended treatment among patients with stage III colon cancer existed and differed by age in England.<h4>Materials and methods</h4>Using data from cancer registry in England between 2012 and 2016, we included all patients with stage III colon cancer and applied multivariable multinominal logistic regression, including an interaction between age and deprivation, to investigate age-specific socioeconomic inequalities in receipt of the NICE-recommend treatment - surgery combined with adjuvant chemotherapy. We also examined the mediating roles of tumour factors on the inequalities in treatment.<h4>Results</h4>Among 20,368 included patients, socioeconomic inequalities in receipt of the NICE-recommend treatment were observed at all ages but wider in patients aged between 65 and 85 years old. For a 70-year-old patient, the probability of receiving the NICE-recommend treatment was 70.8% (95% CI: 68.6, 73.1) for the least vs. 59.4% (53.7, 65.1) for the most deprived quintile. When both groups were unlikely to receive the NICE-recommended treatment (85+ years old), patients from less deprived areas had a higher probability of receiving some alternative treatments like surgery while those with the most deprived backgrounds received none. Tumour factors explained little of inequalities in receipt of surgery or adjuvant chemotherapy.<h4>Conclusion</h4>Patients from deprived areas tended to receive inferior treatment options, and tumour factors explained little of these inequalities. Guidelines need to ensure that the NICE-recommended treatment modality is available to all to reduce the survival gap.