Retinoblastoma is a malignant retinal tumor that affects young children. Mutations in the RB1 gene cause retinoblastoma. Mutations in both RB1 alleles within the precursor retinal cell are essential, with one mutation that may be germline or somatic and the second one that is always somatic. Identification of the RB1 germline status of a patient allows differentiation between sporadic and heritable retinoblastoma variants. Application of this knowledge is crucial for assessing short-term (risk of additional tumors in the same eye and other eye) and long-term (risk of nonocular malignant tumors) prognosis and offering cost-effective surveillance strategies. Genetic testing and genetic counseling are therefore essential components of care for all children diagnosed with retinoblastoma. The American Joint Committee on Cancer has acknowledged the importance of detecting this heritable trait and has introduced the letter "H" to denote a heritable trait of all cancers, starting with retinoblastoma (in publication). In this article, we discuss the clinically relevant aspects of genetic testing and genetic counseling for a child with retinoblastoma.