Objective: In this study, we aimed to determine the early stage of cognitive impairment in newly diagnosed Major Depressive Disorder (MDD) patients by comparing them with the healthy control group. The cognitive functions of the people diagnosed with depression, especially attention, psychomotor speed and executive functions that may occur in the determination of the level of impairment was thought to contribute to the development of treatment programs. Method: The study group consisted of 60 patients with untreated MDD who were admitted to the psychiatry outpatient clinic at Adana Mental Health and Diseases Hospital and a control group consisting of 30 people who were not diagnosed with depression similar to age and gender. Patients who had previously been treated with a psychiatric diagnosis and who had a history of drug or psychotherapy during the last 6 months were excluded from the study. Beck Depression Inventory (BDI) and Trail Making Test (TMT) were used as measuring instruments. Results: In the study, it was determined that the deterioration in cognitive functions was significantly higher in the untreated MDD patients than in the healthy control group. TMT scores were significantly different between the patient and the control group (p<0.005). A positive and linear relationship between the clinical severity of depression and the level of cognitive impairment was obtained (A+B time; r=0.52, p<0.01). Discussion: In the early period, cognitive impairment should be considered in patients with MDD and treatments aimed at cognitive impairment should be included.