The purpose of this study was to evaluate the efficacy of a web-based cognitive rehabilitation intervention in survivors of adult-onset cancer and a sample of non-cancer community dwelling adults. Fifty-one participants were recruited and allocated to a cancer intervention group, a non-cancer intervention group, or a non-cancer waitlist group. Intervention groups completed a 4-week online program and all participants were assessed at baseline, post-intervention and 3-month follow-up. The primary outcome measure was subjective cognitive functioning. Secondary outcome measures included objective cognitive functioning, distress, quality of life (QoL), illness perception and program satisfaction. Results from the study found significant improvements on self-report measures of cognitive functioning in both treatment groups, as well as improvements on objective measures assessing attention and executive functioning. No intervention effects were observed for distress, QoL or illness perception. High participant satisfaction was observed with 75% of participants in the cancer group reporting being either satisfied or very satisfied with the program compared to 87% in the non-cancer treatment group. Initial evaluation of the program suggests that the web-based cognitive rehabilitation intervention shows potential for improving subjective and objective cognitive functioning in cancer survivors and community dwelling adults.