Background/aim: This study aimed to determine the relationship between the peripheral blood neutrophil to lymphocyte ratio (NLR) and irritable bowel syndrome (IBS). Materials and methods: A total of 107 patients suffering from constipation-predominant IBS, diagnosed in accordance with the ROMA III criteria and having complete blood count tests, were enrolled in this study. All patients underwent total colonoscopy in order to rule out any probable underlying organic colonic pathology. Results: The control group consisted of 106 healthy people with no medical complaints. The peripheral blood NLR was 2.80 ± 2.52 on average in the IBS group. The NLR average was 2.37 ± 1.65 in the control group, and the average NLR ratio in the patient group was statistically significant (P < 0.03) and higher than that of the control group when the patient and the control groups were compared. Conclusion: Peripheral blood NLR as a reliable, precise indicator of inflammation in constipation-predominant IBS patients, detected with a simple complete blood count, was slightly elevated but statistically significant compared to the control group.