The increased application of germline genetic testing is expanding our understanding of the risk factors associated with childhood cancer development, and, in some cases, such testing is also informing clinical management. Nonetheless, the incorporation of genetic testing into the pediatric oncology setting is complex and associated with many ethical and practical challenges. The decision as to whether to pursue clinical genetic testing for hereditary cancer predisposition for children should always be guided by the best interest of the child. Despite this fundamental ethical principle, patients, parents, and health care providers may differ in their opinions. Clinical genetic testing to detect the presence of predisposition syndromes associated with childhood-onset cancers, particularly those for which surveillance and preventive measures have proven to enhance outcome, is currently well accepted. On the other hand, clinical genetic testing of children for syndromes associated with adult-onset cancers has raised many concerns about the potential for psychological harm and disrespect of patient autonomy. As a consequence, such testing is not encouraged. The challenges surrounding germline genetic testing are further complicated when testing is done in the research setting and/or when it involves whole-exome or whole-genome sequencing approaches, which can uncover genetic variants that may or may not be associated with the disease under study. Accordingly, there is great debate around these processes and the most appropriate approaches regarding the return of test results. Future research is needed to enhance knowledge about how best to incorporate genomic information into clinical practice.