Informal caregivers are the primary source of support for cancer patients, providing assistance with household tasks, medical care and emotional support. These responsibilities often result in high levels of emotional, physical, social and financial burden for the caregiver. The aim of this study was to perform a scoping review exploring what is known regarding the financial costs experienced by caregivers and identify gaps in the literature. Seven databases were searched for articles published between May 2008 and May 2018 related to direct and indirect costs of informal cancer care. Included articles reported on the costs incurred by cancer caregivers as a dollar value, relied on caregiver‐reported costs and were peer reviewed. A total of 19 studies met the inclusion criteria. These studies reported out of pocket costs‚ opportunity costs of informal care time and caregiver time loss from paid employment. Care time was the largest source of cancer caregiver costs, averaging $4,809 per month when valued using the proxy good method or $2,877 per month when the opportunity cost approach was used. Caregiver costs were highest when the care recipient was in the palliative phase of the disease. There was an absence of literature reporting costs for cancer caregivers in low and middle income countries and none of the included studies considered costs related to the caregivers' medical expenditures. There were many challenges when comparing the costs across studies due to variations in the type of expenses reported and the methods used to value expenses. Quantifying the financial costs associated with being an informal caregiver can facilitate the communication of the financial burden caregivers experience, potentially spurring the development of policies and programs to reduce their financial burden and better support cancer caregivers.