Cancer-related cognitive impairment (CRCI) associated with diagnosis and treatment is frequently reported by cancer survivors and has been well documented in the literature. A subset of cancer survivors reports problems with memory, attention, processing speed, executive functioning and other cognitive domains prior to, during, or after completion of primary curative treatments. These cognitive changes can reduce long-term daily functioning and quality of life (QoL). Cognitive rehabilitation therapy (CRT) has been demonstrated to be an effective method for mitigating symptoms of cognitive dysfunction through the re-attainment of cognitive skills lost or altered due to injury and can improve functioning on everyday tasks. The purpose of this research was to adapt an existing CRT program for cancer survivors, ReCog, into a web-based version, eReCog, and evaluate its efficacy in two studies: a pilot study (Study One) and a randomised controlled trial (Study Two). The primary outcome variable in both studies was subjective cognitive functioning, with secondary outcomes being objective cognitive functioning, QoL, psychological distress, and illness perceptions. A secondary aim was to examine the degree to which participants engage in web-based interventions by investigating a new method for quantifying engagement that examines the number of activities completed in the program modules rather than utilising typical methods described in the literature. The final aim of this research project was to investigate potential mediating factors by assessing the psychological needs of competence, autonomy, and relatedness through a Self-Determination Theory (SDT) framework. SDT is a macro theory of human motivation, which purports that self-motivation stems from the extent to which an individual is able to meet innate psychological needs within their social network. As such, human beings strive to maximise their potential through self-movement in order to increase their behavioural functioning over time. These psychological needs have previously been demonstrated to mediate the relationships between intervention programs and improved physical activity, communication, and QoL in cancer survivors. Firstly, it was hypothesised participants in the intervention program would demonstrate significant improvements in subjective cognitive functioning compared to waitlist groups in both studies. Secondly it was expected treatment participants would show improvements on objective cognitive functioning and perform better on outcome measures than waitlisted groups. Lastly it was hypothesised that the effects of treatment on subjective cognitive functioning would be mediated by the variables of competence, autonomy, and relatedness. To test these hypotheses, Study One was conducted with a cohort of cancer survivors, community dwelling adults, and a waitlist non-cancer group, followed by Study Two with cancer survivors assigned to intervention and waitlist groups. A few statistically significant interaction effects on measures of subjective cognitive functioning were found, although many of the improvements were observed in the waitlisted groups as well albeit to a smaller degree. Both improvements and deteriorations were observed on some domains of objective cognitive functioning in both intervention and waitlist groups. Improved QoL was observed in both the intervention and waitlist group in the RCT. Significant changes in competence, autonomy and relatedness were not observed in either study indicating these constructs were not factors that mediated the relationship between treatment and outcome variables. Overall, these results suggest that brief 4-week online cognitive rehabilitation has the potential to improve self-reported cognitive functioning and QoL in cancer survivors.