Background COVID-19 is caused by SARS-CoV-2 and has a wide range of symptoms. While Diabetes Mellitus (DM) is a common comorbidity in COVID-19 patients, it is the main comorbidity in non-surviving COVID-19 patients. Interleukin-8 (IL-8) is a cytokine that has been correlated with severity and mortality in COVID-19 patients, but its role in COVID-19 patients with DM comorbidity and its relationship with NLR and CRP as markers of inflammation are not yet fully understood. Objective To investigate the correlation between IL-8, NLR, and CRP in COVID-19 patients with DM comorbidity. Methods A cross-sectional study was conducted at the Integrated Infectious Disease Installation of Dr. Saiful Anwar Malang Hospital from June to November 2021 using consecutive sampling. IL-8 was measured using the ELISA method with Legendmax ® Human IL-8. NLR was measured using flow cytometry, while CRP was measured using the immunoturbidimetric method with Cobas C6000 ® . Patient outcomes were obtained from medical records. Results A total of 124 research subjects participated in the study. IL-8 and CRP levels were significantly higher (p < 0.05) in COVID-19 patients with DM comorbidity, and were also significantly higher (p < 0.05) in non-surviving COVID-19 patients. Overall, there was a positive correlation between IL-8 and CRP (r = 0.58, p < 0.05). There was also a positive correlation between IL-8 (r = 0.58; p < 0.05), NLR (r = 0.45, p < 0.05), CRP (r = 0.54, p < 0.05) and mortality in COVID-19 patients with DM comorbidity. The presence of DM comorbidity increased IL-8 levels and aggravated inflammation in COVID-19 patients, thereby increasing the risk of mortality. Conclusion IL-8, CRP and NLR levels were higher in non-surviving COVID-19 patients with DM comorbidity, indicating that they could serve as good predictors of poor outcomes in this patient population.