Hereditary retinoblastoma (Rb) is a high penetrance autosomal dominant disease showing not only an increased risk of suffering bilateral Rb but also other second neoplasms. However, some families show a low-penetrance phenotype with reduced expressivity and incomplete penetrance of the retinoblastoma gene (RB1). Given the lack of specific guidelines for the follow-up of adult patients with hereditary Rb, the authors present a case report of a family with a low-penetrance phenotype and review the recommended surveillance in this setting, stressing the difficulties found in the genetic counselling process and follow up. Thus, since patients are at an increased risk, lifelong regular medical surveillance to detect any second malignancy at a stage that can be cured is required. In addition, avoidance of DNA-damaging agents and genetic testing should be considered for a throughout management of these families.