Objective: Working memory (WM) deficits are highly prevalent in multiple sclerosis (MS). Damage to white matter tracts has been shown to contribute to decreased WM performance. However, most studies have only focused on what the “number correct” can tell us about the brain-behavior relationship. The current study investigated errors in WM performance in relation to structural white matter damage in MS. Method: Forty-eight individuals (15m, 33f) with MS were administered the PASAT (3s version) as a measure of WM. Number correct, number of commission errors, and number of omission errors were calculated. Participants were scanned during a diffusion tensor imaging (DTI) protocol. Several measures of white matter integrity - FA, radial diffusivity (RD), and axial diffusivity (AD) - were calculated for three white matter tracts: forceps minor (FM), superior longitudinal fasciculus (SLF), and the cingulum. Results: Correlational analyses were conducted. Results showed that ‘errors of commission’ was the best predictor of white matter damage in MS patients. That is, errors of commission significantly predicted decreased FA and increased RD and AD in the cingulum and FM. Number correct and errors of omission did not predict white matter damage in these tracts. Conclusion: To the authors' knowledge, this is the first study to investigate the predictive power of error measures of WM in MS. Errors of commission are thought to reflect working memory impairment and possibly other cognitive disturbances, such as perseveration and impulsivity. Therefore, it may be beneficial to take error measures into consideration when evaluating WM dysfunction.