This study examined the influence of processing speed (PS) on benefit from treatment with the Kessler Foundation modified Story Memory Technique® (KF-mSMT®), a cognitive rehabilitation intervention shown to improve new learning and memory in traumatic brain injury (TBI). Non-profit research center 62 participants with moderate-to-severe TBI were included, 31 assigned to the treatment group and 31 to the placebo-control group. Double-blind, placebo-controlled, randomized clinical trial. The present study represents a post-hoc analysis to examine the role of PS on treatment efficacy. Baseline and follow-up neuropsychological assessment including the California Verbal Learning Test, Second Edition (CVLT-II), Memory Assessment Scales - Prose Memory (MAS-PM) and the Symbol Digit Modalities Test (SDMT). A treatment effect was not observed on the CVLT-II learning slope in the treatment group relative to the placebo group post-treatment, after co-varying for education, baseline CVLT slope and PS performance. However, performance on a measure of PS, the SDMT, was a significant predictor of post-treatment change following KF-mSMT® treatment. PS was not a significant predictor of benefit from treatment as documented by the MAS-PM immediate or delayed recall score, both of which showed a significant treatment effect. Performance on measures of cognitive dysfunction aside from learning and memory impact the benefit from KF-mSMT® treatment. Implications for cognitive rehabilitation for individuals with TBI are discussed.