Objectives: . Calprotectin, a protein released by neutrophils, has been used in many studies as a biomarker showing the presence of inflammation. In this study, it was aimed to investigate the relationship between serum calprotectin level and response to the treatment of idiopathic sudden sensorineural hearing loss (ISSHL). Methods: . The present study is a prospective, cross-sectional historical cohort study. The study group consisted of 44 patients with ISSHL, and the control group consisted of 41 healthy volunteers without ear pathology. At the same time, patients in the study group were divided into three groups according to the response to ISSHL treatment (recovered, partially recovered, unrecovered). The relationship between the groups was statistically evaluated in terms of serum calprotectin levels. Results: . The mean serum calprotectin value was 75.67±19.48 ng/mL in the study group and 50.24±29.14 ng/mL in the control group (P=0.001). Serum calprotectin value according to the severity of hearing loss in the mild, moderate and severe was 66.20±8.82, 70.35±16.77, and 91.23±19.73 ng/mL, respectively. Serum calprotectin value in the severe group was significantly higher compared to the moderate and mild groups (P=0.004, P=0.001, respectively). Serum calprotectin value according to the treatment response in the recovered, partially recovered and unrecovered groups was 63.36±11.54, 80.17±12.06, and 85.33±22.33 ng/mL, respectively. Serum calprotectin value in the recovered group was significantly lower compared to the partially recovered and unrecovered groups (P=0.002, P=0.001, respectively). Conclusion . Serum calprotectin value informs the clinician about both the severity of hearing loss and the response to treatment. Hence, serum calprotectin can be used as an important biomarker in ISSHL patients for the determination of the prognosis of disease.