Objective: Examined whether Stroop-Color Word trial scores mediated the relationship between Processing Speed Index scores of the WAIS-IV and Immediate Memory Index scores on the WMS-IV. Method: A total of 185 individuals with a mean age of 29.20 years (SD = 12.30) were included in the current study. Participants were part of a larger archival database from an outpatient neuropsychology clinic. Demographics included 40.8% males and 59.2% females with a mean of 15.59 (SD = 2.03) years of education. Participants were given the Stroop Color Word (SCW), WAIS-IV, and WMS-IV as part of a comprehensive neuropsychological battery. Results: Bootstrapping multiple mediation effects using Hayes (2008) PROCESS approach for SPSS were utilized to test the model using 5,000 bootstrap samples. Significance level was set to the .05 level. Total and direct effects of Processing Speed Index and Immediate Memory Index scores were B = .237, p < .001 and B = .181, p = .009, respectively. Bootstrapping indirect effects were significant for SCW (B = .056, CI 95%: .018, .124). Sobel's test of point estimates was also found to be significant (B = .057, p = .031). Conlusion: Results suggested that focused attention, mental flexibility, and inhibition of prepotent responses mediate the relationship between processing speed and immediate memory skills. Selectively attending to specific tasks and inhibition of internal and external stimuli is important for encoding information to be remembered following a short delay. The faster one is able to process material, the better they would be at inhibiting specific responses; therefore, individuals are able to encode information efficiently. In patients with ADHD, deficits in inhibition and focused attention may underlie reported difficulty remembering different types of information.