People that develop extra-cranial cancers often display comorbid neurological disorders, such as anxiety, depression, and cognitive impairment, even before commencement of chemotherapy. This suggests bidirectional crosstalk between non-central nervous system tumours and the brain, which can regulate peripheral tumour growth. However, the reciprocal neurological effects of tumour progression on brain homeostasis are not well understood. Here, we review brain regions involved in regulating peripheral tumour development and how they, in turn, are adversely impacted by advancing tumour burden. Tumour-induced activation of the immune system, blood-brain-barrier breakdown, and chronic neuroinflammation can lead to circadian rhythm dysfunction, sleep disturbances, aberrant glucocorticoid production, decreased hippocampal neurogenesis and dysregulation of neural network activity, resulting in depression and memory impairments. Given that cancer-related cognitive impairment decreases the efficacy of chemotherapy, diminishes patient quality of life, and worsens cancer prognosis, it is essential that more research is focused at understanding how peripheral tumours impact brain homeostasis.