Background: The International Society for Bipolar Disorders Targeting Cognition Task Force recommends the Screen for Cognitive Impairment in Psychiatry (SCIP) to screen for cognitive impairment in bipolar disorder. However, SCIP must be administered by a healthcare professional, which is often impossible due to time and resource constraints. Web-based, self-administered cognition screening tools may enable assessment and monitoring of patients’ cognition at a much larger scale to a reduced cost. For this purpose, we developed the Internet-Based Cognitive Assessment Tool (ICAT) as a modified web-based version of SCIP. This study aimed to investigate the sensitivity and validity of ICAT for cognition assessment in bipolar disorder. Method: Thirty-five patients with bipolar disorder in full or partial remission and 35 healthy controls completed ICAT on a computer, the standard paper-and-pencil SCIP and a subjective cognition questionnaire and were rated for mood symptoms and functioning at the Copenhagen Affective Disorders Research Centre. Results: Patients displayed cognitive impairments compared to controls on the ICAT (t (61)=3.67, p<.001, d=0.93). There was a strong correlation between ICAT and SCIP Total Scores (r(61)=.72, p<.000) and moderate to strong correlations on subtest scores (r=.48-.63, ps<.001). Across all participants, lower ICAT scores correlated with more subjective cognitive complaints (r(59)=-.43, p<.001) and poorer psychosocial functioning (r(62)=-.47, p<.001). Conclusion: ICAT is a sensitive and valid web-based tool for cognition assessment in patients with bipolar disorder. This highlights ICAT as a novel web-based cognition screening tool that is feasible for largescale assessment and monitoring of cognition in the clinical management of bipolar disorder.