Managing fear of cancer recurrence or progression (FCR/P) is one of the most common unmet needs among cancer patients and survivors. While some fear is an adaptive in response to a cancer diagnosis, for 60% of people FCR/P reaches clinically significant levels and for 20% FCR/P becomes severe. FCR/P is characterized by persistent worry, preoccupation with bodily checking for signs of cancer, frequent need for reassurance from hospital services and future planning difficulties. Left untreated, high FCR/P persists over time and can adversely affect screening and follow-up behaviours, is associated with increased anxiety and depression, poorer quality of life and higher healthcare utilisation. While FCR/P is experienced across cancer types, those with poor prognosis tumours and more advanced disease report higher FCR/P as treatment for longer time and frequent monitoring contribute to uncertainty and fear. The content of fears also differs. For example, people with ovarian and brain cancers report greater existential concerns and death anxiety. There are now interventions with efficacy in treating FCR, including psychologist delivered interventions for those with severe FCR and online interventions for people with moderate FCR. However, these interventions have been evaluated with early-stage cancer patients previously treated with curative intent. Further research is required to determine the duration of effect and optimal dosing to inform stepped care models. The effectiveness demonstrated amongst cancer-free survivors has also not been replicated in trials with people with active disease, where fear of progression (FoP) is more prominent. The reported poor engagement and high attrition rates across these studies highlights an urgent need for interventions better tailored to the experiences of those with poor prognosis and the increasing number of people living long term with advanced disease due to targeted and immunotherapies.