Although cognitive problems are an increasingly recognised issue affecting some cancer survivors, mechanisms are poorly understood. The self-regulatory model of illness perceptions shows promise for understanding cognitive issues for cancer survivors but has not previously been applied in this population. This study was the first to examine illness perceptions regarding cognitive function for cancer survivors. Survivors responded to open-ended questions regarding perceived cognitive problems and their impact. In addition, associations among objective and subjective cognition, psychosocial distress, quality of life, and illness perceptions were examined. Participants were 32 survivors of adult-onset non-CNS tumours (comprising 23 participants who completed a cognitive rehabilitation intervention and 9 participants who completed assessments only) plus a matched community sample of 23 adults with no cancer history. Standardised measures assessed objective and subjective cognition, psychosocial distress, quality of life, and illness perceptions. Cancer survivors who reported poor subjective cognitive function were also significantly more likely to report psychosocial distress, low quality of life and to view their impairment as having high consequences and emotional impact, and had a stronger identification with cognitive impairment. It was noted that while there was an expected discrepancy between objective and subjective cognitive function for the intervention group, this did not hold true for either comparison group. Illness perceptions appeared to play a role in influencing the associations between objective and subjective cognitive function for cancer survivors. This finding suggests that illness perceptions may play a key mediating or moderating role between subjective and objective cognition and offers novel evidence that illness perceptions may be a key component missing from current models of cognitive dysfunction for cancer survivors. It is hoped that this study can provide a valuable stepping stone towards further research into the factors which influence subjective and objective cognition function for cancer survivors.