To validate the THINC-integrated tool (THINC-it)-a freely available, patient-administered, computerized screening tool integrating subjective and objective measures of cognitive function in adults with major depressive disorder (MDD). Subjects aged 18 to 65 years (n = 100) with recurrent MDD experiencing a major depressive episode of at least moderate severity were evaluated and compared to age-, sex-, and education-matched healthy controls (n = 100). Between January and June 2016, subjects completed the THINC-it, which includes variants of the Choice Reaction Time Identification Task (IDN), One-Back Test, Digit Symbol Substitution Test, Trail Making Test-Part B, and the Perceived Deficits Questionnaire for Depression-5-item (PDQ-5-D). The THINC-it required approximately 10 to 15 minutes for administration and was capable of detecting cognitive deficits in adults with MDD. A total of 44.4% of adults with MDD exhibited cognitive performance at ≥ 1.0 SD below that of healthy controls on standardized mean scores of the THINC-it. Concurrent validity of the overall tool, based on a calculated composite score, was acceptable (r = 0.539, P < .001). Concurrent validity of the component tests ranged from -0.083 (IDN) to 0.929 (PDQ-5-D). Qualitative survey results indicated that there was a high level of satisfaction and perceived value in administering the THINC-it regarding its impact on the appropriateness and quality of care being received. The THINC-it is a valid and sensitive tool for detecting cognitive dysfunction in adults with MDD that is free, easy to use, and rapidly administered. The THINC-it should be incorporated into the assessment and measurement of all patients with MDD, particularly among those with enduring functional impairment. ClinicalTrials.gov identifier: NCT02508493.